Human beings are complex animals; which have a complex digestive system. The human digestive system is composed of an alimentary canal and some accessory glands. The alimentary canal is divided into several parts, viz. oesophagus, stomach, small intestine, large intestine, rectum and anus. Salivary gland, liver and pancreas are the accessory glands which lie outside the alimentary canal.
Nutrition in Amoeba
Amoeba is a unicellular animal which follows holozoic mode of nutrition. The cell membrane of amoeba keeps on protruding into pseudopodia. Amoeba surrounds a food particle with pseudopodia and makes a food vacuole. The food vacuole contains the food particle and water. Digestive enzymes are secreted in the food vacuole and digestion takes place. After that, digested food is absorbed from the food vacuole. Finally, the food vacuole moves near the cell membrane and undigested food is expelled out.
Steps of Holozoic Nutrition Steps of Holozoic Nutrition
Ingestion: The process of taking in the food is called ingestion.
Digestion: The process of breaking complex food substances into simple molecules is called digestion. Simple molecules; thus obtained; can be absorbed by the body.
Absorption: The process of absorption of digested food is called absorption.
Assimilation: The process of utilization of digested food; for energy and for growth and repair is called assimilation.
Egestion: The process of removing undigested food from the body is called egestion.
Animal Nutrition
1. Heterotrophic Nutrition: When an organism takes food from another organism, it is called heterotrophic nutrition. Different heterotrophic organisms follow different methods to take and utilize food. Based on this, heterotrophic nutrition can be divided into two types:
2. Saprophytic Nutrition: In saprophytic nutrition, the digestion of food takes place before ingestion of food. This type of nutrition is usually seen in fungi and some other microorganisms. The organism secretes digestive enzymes on the food and then ingests the simple substances. Saprophytes feed on dead materials and thus help in decomposition dead remains of plants and animals.
3. Holozoic Nutrition: In holozoic nutrition, the digestion of food follows after the ingestion of food. Thus, digestion takes place inside the body of the organism. Holozoic nutrition happens in five steps, viz. ingestion, digestion, absorption, assimilation and egestion.
Significance of Photosynthesis
● Photosynthesis is the main way through which the solar energy is made available for different living beings.
● Green plants are the main producers of food in the ecosystem. ● All other organisms directly or indirectly depend on green plants for food.
● The process of photosynthesis also helps in maintaining the balance of carbon dioxide and oxygen in the air.
Steps of Photosynthesis
1. Sunlight activates chlorophyll; which leads to splitting of water molecule.
2. The hydrogen; released by splitting of water molecule is utilized for reduction of carbon dioxide to produce carbohydrates.
3. Oxygen is the byproduct of photosynthesis.
4. Carbohydrate is subsequently converted into starch and is stored in leaves and other storage parts.
5. The splitting of water molecules is part of the light reaction.
6. Other steps are part of the dark reaction during photosynthesis.
How do raw materials for photosynthesis become available to the plant?
Water comes from soil; through the xylem tissue in roots and stems.
Carbon dioxide comes in the leaves through stomata.
Plant Nutrition
Green plants prepare their own food. They make food in the presence of sunlight. Sunlight provides energy. carbon dioxide and water are the raw materials. Chloroplast is the site where food is made.
Photosynthesis: The process by which green plants prepare food is called photosynthesis. During this process; the solar energy is converted into chemical energy and carbohydrates are formed. Green leaves are the main sites of photosynthesis. The green portion of the plant contains a pigment chloroplast; which contains chlorophyll. The whole process of photosynthesis can be shown by following equation:
6CO2 + 6H2O ⇨ C6H12O6 + 6O2
Types of Nutrition
1. Autotrophic Nutrition: The mode of nutrition in which an organism prepares its own food is called autotrophic nutrition. Green plants and blue-green algae follow the autotrophic mode of nutrition.
2. Heterotrophic Nutrition: The mode of nutrition in which an organism takes food from another organism is called heterotrophic nutrition. Organisms; other than green plants and blue-green algae follow heterotrophic mode of nutrition. Heterotrophic nutrition can be further divided into two types, viz. saprophytic nutrition and holozoic nutrition.
Saprophytic Nutrition: In saprophytic nutrition; the organism secretes the digestive juices on the food. The food is digested while it is still to be ingested. The digested food is then ingested by the organism. All the decomposers follow saprophytic nutrition. Some insects; like houseflies; also follow this mode of nutrition.
Holozoic Nutrition: In holozoic nutrition; the digestion happens inside the body of the organism, i.e. after the food is ingested. Most of the animals follow this mode of nutrition.
Nutrition
The process by which an organism takes food and utilizes it is called nutrition.
Need of nutrition: Organisms need energy to perform various activities. The energy is supplied by the nutrients. Organisms need various raw materials for growth and repair. These raw materials are provided by nutrients.
Nutrients: Materials which provide nutrition to organisms are called nutrients. Carbohydrates, proteins and fats are the main nutrients and are called macronutrients. Minerals and vitamins are required in small amounts and hence are called micronutrients.
Life Process
Various functions carried out by living beings; which are necessary to maintain and continue life are called life process. Following are the life processes in living beings:
1. Nutrition
2. Respiration
3. Transportation of substances
4. Excretion
5. Movement
6. Reproduction
How do the terrestrial plants get water for photosynthesis?
Water used in photosynthesis is taken up from the soil by the roots in terrestrial plants. It is transported to the leaves through the xylem tissues.
Distinguish between a parasite and a saprotrophs?
Parasite
• A parasite takes readymade food from the organism on which it feeds.
• They feed on a living organism.
• The organism on which it feeds is called host.
• It deprives the host of valuable nutrients.
Saprotrophs
• They secrete the digestive juices on the matter they live and convert it into a solution and then absorb it.
• They feed on dead and decaying organism.
• They do not feed on a living organism.
• There is no host at all.
What is digestion?
The process of breaking down complex food substances into simple molecules is called as digestion.
What does the human digestive tract consists of?
Digestive system in human beings consists of alimentary canal and digestive glands.
Alimentary canal is made up of mouth, buccal cavity, pharynx, oesophagus, stomach, intestine, rectum and anus.
The digestive glands are the salivary glands, the gastric glands, the liver, the pancreas and the intestinal glands.
How do plants obtain carbon-dioxide for photosynthesis?
Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves. Such pores are called stomata. Massive amounts of gaseous exchange takes place in the leaves through these pores for the purpose of photosynthesis. These pores are surrounded by ‘guard cells’. Since large amounts of water can also be lost through these stomata, the plant closes these pores when it does not need carbon dioxide for photosynthesis. The opening and closing of the pore is a function of the guard cells.
How do plants obtain nitrogen?
Nitrogen is an essential element used in the synthesis of proteins and other compounds. This is taken up in the form of inorganic nitrates or nitrites. Or it is taken up as organic compounds which have been prepared by bacteria from atmospheric nitrogen. Atmospheric nitrogen is fixed by leguminous plants with the help of symbiotic bacteria present in the root nodules of these plants.
What is the role of stomach in digestion?
The stomach is divided into three compartments namely cardiac, fundus and pylorus. The junction of oesophagus and stomach is guarded by valve which does not allow the food to travel in backward direction.
• In the stomach, food is mixed with the gastric juices secreted by the gastric glands.
• Gastric juice is a combination of hydrochloric acid, enzymes like pepsin, lipase and mucous.
• Partially digested food in the stomach becomes acidic and is known as chyme.
What is the function of the small intestine?
The three main categories of nutrients that undergo digestion within the small intestine are proteins, lipids (fats) and carbohydrates. The small intestine is divided into duodenum, ileum and jejunum.
The intestinal enzymes such as invertase, maltase and lipase act upon partially digested proteins, carbohydrates and fats.
Proteins and peptides → amino acids
Lipids (fats) → fatty acids and glycerol
Some carbohydrates → simple sugars, or monosaccharides (e.g., glucose).
• Proteins, carbohydrates and fats are simplified into amino acids, glucose, fatty acids and glycerol in a liquid medium known as chyle.
• Specific structures called as villi in the small intestine increase its surface area to ensure efficient and rapid absorption of nutrients. Blood capillaries in the villi absorb nutrients and transport the food to all the cells in the body.
• Other carbohydrates pass undigested into the large intestine where they may, depending on their type, be broken-down by intestinal bacteria.
How do plants obtain nitrogen?
Nitrogen is an essential element used in the synthesis of proteins and other compounds. This is taken up in the form of inorganic nitrates or nitrites. Or it is taken up as organic compounds which have been prepared by bacteria from atmospheric nitrogen. Atmospheric nitrogen is fixed by leguminous plants with the help of symbiotic bacteria present in the root nodules of these plants.
How will you prove that sunlight is essential for photosynthesis and the food prepared by green plants using photosynthesis is starch?
Let us do an activity to prove that sunlight is necessary for photosynthesis-
• We take a potted plant having green leaves and place it in a completely dark place for about three days to destarch its leaves. So, in the beginning of the experiment, the leaves do not have any starch in them.
• Take a thin strip of aluminium foil (or black paper) and wrap it in the centre of one leaf on both the sides (while the leaf is still attached to the plant). The aluminium foil should be fixed tightly to the leaf by using paper clips so that sunlight may not enter it from the sides. The aluminium foil should cover only a small part of the leaf so that the remaining part of the leaf remains uncovered and exposed to sunlight. We have covered the centre part of the leaf with aluminium foil so that sunlight may not fall on this covered part of the leaf.
• Keep this potted plant (with partially covered leaf) in bright sunshine for three to four days.
• Pluck the partially covered leaf from the plant and remove its aluminium foil. Immerse this leaf in boiling water for a few minutes. This will break down the cell membranes of leaf cells and make the leaf more permeable to iodine solution (so that it may reach the starch present inside the leaf cells).This leaf is now to be tested for the presence of starch. But before testing for starch, chlorophyll has to be removed from the leaf. This is because chlorophyll interferes in the test for starch due to its green colour.
• Put the plucked leaf in a beaker containing some alcohol. Place the beaker containing alcohol and leaf in a water bath. A water bath is being used here for heating alcohol because alcohol is a highly inflammable liquid.
• Heat the water in the bigger beaker (or water bath). Now, the alcohol in the smaller beaker will also get heated and start boiling soon. This boiling alcohol will extract (or remove) chlorophyll from the green leaf.
• Boil the green leaf in alcohol till all its green pigment 'chlorophyll' is removed. The leaf will now become almost colourless or pale (and the alcohol will turn green).
• Remove the colourless leaf from alcohol and wash it thoroughly with hot water to soften it and remove any chlorophyll which may be sticking to it.
• Place the colourless leaf in a petri-dish. Drop iodine solution over the decolourised leaf with the help of a dropper. Observe the change in colour of leaf.
• The middle part of leaf which was covered with aluminium foil does not turn blue-black on adding iodine solution showing that no starch is present in this middle part of the leaf. This is because sunlight could not reach the covered 'middle part' of the leaf due to which the covered 'middle part' of leaf could not do photosynthesis to make starch.
• The uncovered part of leaf (on both sides of the aluminium foil) which was exposed to sunlight turns blue-black on adding iodine solution showing that starch is present in this part of leaf. This means that the part of leaf which was exposed to sunlight could do photosynthesis to make starch.
Since the part of leaf which was covered and hidden from sunlight does not contain starch but the part of leaf which was exposed to sunlight contains starch, therefore, we conclude that sunlight is necessary for photosynthesis (to make food like starch).
From the above experiment, we actually get two conclusions-
(i) Sunlight is necessary for the process of photosynthesis, and
(ii) Leaves make starch as food by photosynthesis.
How do plants obtain carbon-dioxide for photosynthesis?
Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves. Such pores are called stomata. Massive amounts of gaseous exchange takes place in the leaves through these pores for the purpose of photosynthesis. These pores are surrounded by ‘guard cells’. Since large amounts of water can also be lost through these stomata, the plant closes these pores when it does not need carbon dioxide for photosynthesis. The opening and closing of the pore is a function of the guard cells.
What are the important events that occur during the process of photosynthesis?
The following events occur during this process -
(i) Absorption of light energy by chlorophyll.
(ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
(iii) Reduction of carbon dioxide to carbohydrates.
These steps need not take place one after the other immediately. For example, desert plants take up carbon dioxide at night and prepare an intermediate which is acted upon by the energy absorbed by the chlorophyll during the day.
What is meant by photosynthesis?
It is the process by which autotrophs (green plants) make their own food from carbon dioxide and water which is converted into carbohydrates in the presence of sunlight and chlorophyll. During this process, oxygen gas is released.
What are the raw materials for photosynthesis?
The raw materials and other necessary items required for photosynthesis are Sunlight, Water, CO2 and Chlorophyll.
What are the two types of heterotrophic nutrition?
Heterotrophic nutrition can be further divided into two types, viz. saprophytic nutrition and holozoic nutrition.
Saprophytic Nutrition: In saprophytic nutrition, the organism secretes the digestive juices on the food. The food is digested while it is still to be ingested. The digested food is then ingested by the organism. All the decomposers follow saprophytic nutrition. Some insects like houseflies also follow this mode of nutrition.
Holozoic Nutrition: In holozoic nutrition, the digestion happens inside the body of the organism, i.e. after the food is ingested. Most of the animals follow this mode of nutrition. Holozoic nutrition happens in five steps, viz. ingestion, digestion, absorption, assimilation and egestion.
What are the types of nutrition?
Types of Nutrition:
Autotrophic Nutrition: The mode of nutrition in which an organism prepares its own food is called autotrophic nutrition. Green plants and blue-green algae follow the autotrophic mode of nutrition.
Heterotrophic Nutrition: The mode of nutrition in which an organism takes food from another organism is called heterotrophic nutrition. Organisms; other than green plants and blue-green algae follow heterotrophic mode of nutrition.
What are nutrients?
Nutrients: Materials which provide nutrition to organisms are called nutrients. Carbohydrates, proteins and fats are the main nutrients and are called macronutrients. Minerals and vitamins are required in small amounts and hence are called micronutrients.
What is meant by life processes?
Various functions carried out by living beings; which are necessary to maintain and continue life are called life process. Following are the life processes in living beings:
• Nutrition
• Respiration
• Transportation of substances
• Excretion
• Movement
• Reproduction
What is the need for nutrition?
Organisms need energy to perform various activities. The energy is supplied by the nutrients. Organisms need various raw materials for growth and repair. These raw materials are provided by nutrients.
When we are asleep we are not performing any activity still our life processes are going on. Why?
The maintenance functions of living organisms must go on even when they are not doing anything particular. That is why the life processes are going on even while we are asleep or not performing any activity.
What is meant by nutrition?
Nutrition is the process by which an organism obtains the food from its environment and utilizes it for various life processes like growth, replacement of tissues, energy etc.
Axiom , Postulates and Theorems :-
Axioms are the general statements, postulates are the axioms relating to a particular field.
(2) Statements : A sentence which is either true or false but not both, is called a statement.
eg. (i) 4+9=6 it is a false sentence, so it is a statement.
(ii) Sanjay is tall. This is not a statement because he may be tall for certain persons and may not be taller for others.
(3) Theorems: A statement that requires a proof is called a theorem.
eg. (i) The sum of the angles of triangle is 1800.
(ii) The angles opposite to equal sides of a triangles are equal.
Corollary - Result deduced from a theorem is called its corollary.
(4) Postulates :- The basic assumptions in geometry which are universal true and are accepted without proof are called Postulates.
(5) Euclid's five postulates are.
(i) A straight line may be drawn from any one point to any other point.
(ii) A terminated line can be produced indefinitely.
(iii) A circle can be drawn with any centre and any radius.
(iv) All right angles are equal to one another.
(v) If a straight line falling on two straight lines makes the interior angles on the same side of it taken together less than two right angles, then the two straight lines, if produced indefinitely meet on that side on which the angles are less than two right angles.
Coefficients
In the polynomial , coefficient of respectively and we also say that +1 is the constant term in it.
Degree of a polynomial in one variable : In case of a polynomial in one variable the highest power of the variable is called the degree of the polynomial.
Classification of polynomials on the basis of degree.
degree Polynomial Example
(a) 1 Linear
(b)2 Quadratic etc.
(c)3 Cubic etc.
(d)4 Biquadratic
Classification of polynomials on the basis of no. of terms
No. of terms Polynomial Examples.
(i) 1 Monomial - etc.
(ii) 2 Binomial - etc.
(iii)3 Trinomial - etc.
Variables
A symbol which may be assigned different numerical values is known as variable.
Example :C - circumference of circle
r - radius of circle
Where 2 & are constants. while C and r are variable
Polynomials
An algebraic expression in which the variables involved have only non-negative integral powers is called a polynomial.
(i) is a polynomial in variable x.
(ii) is an expression but not a polynomial.
Polynomials are denoted by
Constant polynomial: A polynomial containing one term only, consisting a constant term is called a constant polynomial. The degree of non-zero constant polynomial is zero.
Zero polynomial: A polynomial consisting of one term, namely zero only is called a zero polynomial.
The degree of zero polynomial is not defined.
Zeroes of a polynomial: Let be a polynomial. If then we say that is a zero of the polynomial p(x).
Remark: Finding the zeroes of polynomial p(x) means solving the equation p(x)=0.
Remainder Theorem: Let be a polynomial of degree and let a be any real number. When is divided by then the remainder is
Factor Theorem: Let be a polynomial of degree and let a be any real number.
(i) If
(ii)
Factor: A polynomial is called factor of divides exactly.
Factorization: To express a given polynomial as the product of polynomials each of degree less than that of the given polynomial such that no such a factor has a factor of lower degree, is called factorization.
Algebraic expressions
A combination of constants and variables connected by some or all of the operations +, -, X and is known as algebraic expression.
Example : etc.
Variables
A symbol which may be assigned different numerical values is known as variable.
Example :C - circumference of circle
r - radius of circle
Where 2 & are constants. while C and r are variable
Constants
: A symbol having a fixed numerical value is called a constant.
Example : 7, 3, -2, 3/7, etc. are all constants
Axiom , Postulates and Theorems :-
Axioms are the general statements, postulates are the axioms relating to a particular field.
(2) Statements : A sentence which is either true or false but not both, is called a statement.
eg. (i) 4+9=6 it is a false sentence, so it is a statement.
(ii) Sanjay is tall. This is not a statement because he may be tall for certain persons and may not be taller for others.
(3) Theorems: A statement that requires a proof is called a theorem.
eg. (i) The sum of the angles of triangle is 1800.
(ii) The angles opposite to equal sides of a triangles are equal.
Corollary - Result deduced from a theorem is called its corollary.
(4) Postulates :- The basic assumptions in geometry which are universal true and are accepted without proof are called Postulates.
(5) Euclid's five postulates are.
(i) A straight line may be drawn from any one point to any other point.
(ii) A terminated line can be produced indefinitely.
(iii) A circle can be drawn with any centre and any radius.
(iv) All right angles are equal to one another.
(v) If a straight line falling on two straight lines makes the interior angles on the same side of it taken together less than two right angles, then the two straight lines, if produced indefinitely meet on that side on which the angles are less than two right angles.
Types of Angles
(1)Acute angle - An acute angle measure between 00 and 900.
(2)Right angle - A right angle is exactly equal to 900.
(3)Obtuse angle - An angle greater than 900 but less than 1800.
(4)Straight angle - A straight angle is equal to 1800.
(5)Reflex angle - An angle which is greater than 1800 but less than 3600 is called a reflex angle.
(6)Complementary angles - Two angles whose sum is 900 are called complementary angles.
(7)Supplementary angle - Two angles whose sum is 1800 are called supplementary angles.
(8)Adjacent angles - Two angles are adjacent, if they have a common vertex, a common arm and their non common arms are on different sides of common arm.
(9)Linear pair - Two angles form a linear pair, if their non-common arms form
a line (a straight angle).
(10)Vertically opposite angles - Vertically opposite angles are formed when two lines intersect each other at a point.
Types of Angles
(1)Acute angle - An acute angle measure between 00 and 900.
(2)Right angle - A right angle is exactly equal to 900.
(3)Obtuse angle - An angle greater than 900 but less than 1800.
(4)Straight angle - A straight angle is equal to 1800.
(5)Reflex angle - An angle which is greater than 1800 but less than 3600 is called a reflex angle.
(6)Complementary angles - Two angles whose sum is 900 are called complementary angles.
(7)Supplementary angle - Two angles whose sum is 1800 are called supplementary angles.
(8)Adjacent angles - Two angles are adjacent, if they have a common vertex, a common arm and their non common arms are on different sides of common arm.
(9)Linear pair - Two angles form a linear pair, if their non-common arms form
a line (a straight angle).
(10)Vertically opposite angles - Vertically opposite angles are formed when two lines intersect each other at a point.
Name three famous writers and philosophers who influenced the French- Revolution. What were their ideas?
Ans.
1. Jean Jacques Rousseau – a French Swiss philosopher. His main idea was – man is naturally good and that society of civilisation makes man anxious and unhappy.
2. Mirabeau – he brought about a journal and delivered powerful speeches to the crowds at Versailles.
3. Voltaire – A famous French writer. He exposed the evils prevailing in the Church and administration. The numbers of the first two estates were the
(i) Clergy and (ii) Nobility respectively.
Discuss the participation of women in political clubs, their activities and demands.
Ans.
1-Women played important role regarding various activities. In order to discuss and voice their interests women started their own political clubs and newspapers. About sixty women’s clubs came up in different French cities.
2.The Society of Revolutionary and Republican Women was the most famous of them, their main demands were that
(a) Women should be given the same political rights as men.
(b) They demanded the right to vote, to be elected to the Assembly and to hold political office.
Describe the importance of Declaration of the Right of Man in France.
Ans
1-The Declaration of the Right of Man in France was a landmark decision in the history of France.
2- The constitution began with a declaration of the Rights of Man and Citizen. Rights such as the right to life, freedom of speech, freedom of opinion, equality before law, were established as ‘natural and inalienable’ rights. That is, they belonged to each human being by birth and could not be taken away
.3- It was the duty of the state to protect each citizen's natural rights. The declaration of the Right of Man and Citizens influenced revolutionary movements elsewhere too.
What landmark decisions were taken by the National Assembly led by the Third Estate on 4th August, 1789.
Ans.
1- Louis XVI finally accorded recognition to the National Assembly and accepted theprinciple that his powers would be checked by a constitution.
2- On 4 August 1789, the Assembly passed a decree abolishing the feudal system of obligations and taxes. Members of the clergy too were forced to give up their privileges
.3- Tithes were abolished and lands owned by the church were confiscated. As a result, the government acquired assets worth at least 2, billion lives.
Describe the causes for the fall of Jacobin government in France.
Ans.
(i) The Jacobin government in France was based on extreme measures. The period from 1793-1794 is referred to as the reign of terror. Robespierre followed a policy of severe Control and punishment.
(ii)All those he saw as being ‘enemies’ of the republic nobles and clergy, members of other political parties, even members of his own party who did not agree with his methods–were arrested, imprisoned and guillotined. This led to chaos and resentment among the people.
(iii)Robespierre’s government ordered shutting down of churches and converting church buildings into barricades or offices. Thus the clergy turned against the Jacobin regime and hastened its fall.
(iv) Robespierre pursued his policies so relentlessly that even his supporters turned against him. They began to demand moderation and a middle path. Finally, he himself was tried by a court in July 1794, arrested and guillotined.
write short note on Jacobins?
Ans.
1- They got their name from the former convent of St. Jacob in Paris.
2-They belonged to the less prosperous sections of the society.
3-They included small shopkeepers, artisans such as shoemakers, pastry cooks, watch-makers, printers, as well as servants and daily wage earners.
4-Their leader was Maximilian Robespierre.
5-A large group among the Jacobin decided to wear long striped trousers similar to those worn by dock workers.
6-This was to set themselves apart from the fashionable sections of society especially the nobles who wore knee breeches.
Name three famous writers and philosophers who influenced the French- Revolution. What were their ideas?
Ans.
1. Jean Jacques Rousseau – a French Swiss philosopher. His main idea was – man is naturally good and that society of civilisation makes man anxious and unhappy.
2. Mirabeau – he brought about a journal and delivered powerful speeches to the crowds at Versailles.
3. Voltaire – A famous French writer. He exposed the evils prevailing in the Church and administration. The numbers of the first two estates were the
(i) Clergy and (ii) Nobility respectively.
Who formed the National Assembly? On what date is ‘Bastille Day’ celebrated and why?
Ans.
1-The representatives of the Third Estate assembled at Versailles on 20 June and declared themselves a National Assembly
2-The Bastille Day is celebrated on 14th July every year because on this day the unruly Paris mob stormed and attacked the prison of Bastille which was considered a symbol of terror and despotism.
Who was the people who comprised the Third Estate? Who paid the taxes and to whom?
Ans
1-The people who comprised the Third Estate were big businessmen, merchants, lawyers, peasants, artisans, small peasants, landless labourers and servants.
2- These were 95 per cent of the population. They had to pay taxes to the state. Taxes included taille, tithes and a number of indirect taxes.
Q.9Who formed the National Assembly? On what date is
Explain what a revolution is. In what way did the French Revolution mean different things to different people?
Ans It is an attempt by a large number of people to change the government of a country, especially by violent action.
1. The Third Estate comprising the common men benefitted from the Revolution. The clergy and nobility had to relinquish their power.
2. Their land was confiscated. Their privileges were finished. The people of lower middle class also benefitted.
3. Position of artisans and workers improved.
4. Clergy, feudal lords, nobles and even women were disappointed. The revolution did not bring real equality as everyone was not given the right to vote meaning women who got it finally in 1946.
Why did slavery begin and why was it abolished in French colonies?
Ans 1-.The slave trade began in the 17th century. The colonies in the Caribbean – Martinique, Guadeloupe and San Domingo – were important Suppliers of commodities.
2- But the reluctance of Europeans to go and work in distant and unfamiliar lands meant a shortage of labour on the plantations.
3- Throughout the eighteenth century there was little criticism of slavery in France. The National Assembly did not pass any laws, fearing opposition from businessmen whose incomes depended on the slave trade
4- It was the Convention which in 1794 legislated to free all slaves in the French overseas possessions. This, however, turned out to be a short-term measure. Napoleon reintroduced slavery.
5- Slavery was finally abolished in French colonies in 1848.
What was ‘natural and inalienable rights’?
Ans1-.The constitution began with a Declaration of the Rights of Man and Citizens
2- Rights such as the right to life, freedom of speech, freedom of opinion, equality before law were established as ‘natural and inalienable rights’, i.e., they belonged to each human being by birth and could not be taken away
3-It was the duty of the state to protect each citizen’s natural right.
Describe how the new political system of constitutional monarchy worked in France.
Ans The constitution of 1791 vested the power to make laws in the National Assembly, which was indirectly elected. That is,
1. Citizens voted for a group of electors, who in turn chose the Assembly. Not all citizens, however, had the right to vote.
2. Only men above 25 years of age who paid taxes equal to at least 3 days of a labourer’s wage were given the status of active citizens, that is, they were entitled to vote.
3. The remaining men and all women were classed as passive citizens.
4. To qualify as an elector and then as a member of the Assembly, a man had to belong to the highest bracket of taxpayers.
Describe the incidents that led to the storming of the Bastille.
Ans. 1- National Assembly was busy at Versailles drafting a constitution; the rest of France was seething with turmoil.
2- A severe winter had meant a bad harvest, the price of bread rose. Often bakers exploited the situation and hoarded supplies.
3- After spending hours in long queues at the bakery, crowds of angry women stormed into the shops.
4- At the same time, the king ordered troops to move into Paris. On 14 July, the agitated crowd stormed and destroyed Bastille.
What was the system of voting in the Estates General? What change did the Third Estate want in this system?
Ans. Voting in the Estates General in the past had been conducted
1. According to the principle that each estate had one vote.
2. Members of the Third Estate demanded that voting must now be conducted by the assembly as a whole, where each member would have one vote.
3. This was according to the democratic principles put forward by philosophers like Rousseau in his book, The Social Contract.
what was the subsistence crisis? Why did it occur in France during the Old Regime?
Ans. 1- The population of France was on the rise. It rose from 23 million in 1715 to 28 million in 1789.This led to increase in the demand for food grains.
2-The production of food grains could not keep pace with the demand and the price of bread which was thestaple diet of the majority Rose rapidly.
3- The wages also did not keep pace with the rise in prices. The gap between the Rich and the poor widened. This led to the subsistence crisis.
NAPOLEON
In 1804, Napoleon crowned himself emperor of France. He set out to conquer neighbouring European countries, dispossessing dynasties and creating kingdoms where he placed members of his family. He saw his role as a moderniser of Europe. He was finally defeated at Waterloo in 1815.
WOMEN’S REVOLUTION
From the very beginning, women were active participants in the events which brought about so many changes in the French society. Most women of the third estate had to work for a living.Their wages were lower than those of men. In order to discuss and voice their interests, women started their own political clubs and newspapers. One of their main demand was that women must enjoy the same political rights as men. Some laws were introduced to improve the position of women. Their struggle still continues in several parts of the world.It was finally in 1946 that women in France won the right to vote.
THE OUTBREAK OF THE FRENCH REVOLUTION
The French Revolution went through various stages. When Louis XVI became king of France in1774, he inherited a treasury which was empty. There was growing discontent within the society of the Old Regime.
1789, Convocation of Estates General. The Third Estate forms National Assembly, the Bastille is stormed, peasant revolts in the countryside.
1791 A constitution is framed to limit the powers of the king and to guarantee basic right to all humanbeings.
1792-93France becomes a republic. Jacobin Republic overthrown, a Directory rules France.
1795 A new Convention appointed a five-man Directorate to run the state from 26 October, 1795.
1799 The Revolution ends with the rise of Napoleon Bonaparte.
Time Line: The French Revolution
1770s-1780s — Economic decline: French Government in deep debt.
1788-1789 — Bad harvest, high prices, food riots
1789, May 5 — Estates-General convened, demands reforms.
1789, July 14 — National Assembly formed. Bastille stormed on July 14. French Revolution starts.
1789, August 4 — Night of August 4 ends the rights of the aristocracy.
1789, August 26 — Declaration of the Rights of Man
1790 — Civil Constitution of the Clergy nationalises the Church.
1792 — Constitution of 1791 converts absolute monarchy into a constitutional Monarchy with limited powers.
1792 — Austria and Prussia attack revolutionary France
1793 — Louis XVI and Marie Antoinette are executed.
1792-1794 — The Reign of Terror starts. Austria, Britain, the Netherlands, Prussia and
Spain are at war with France.
— Robespierre’s Committee of Public Safety repels back foreign invaders. Executes many “enemies of the people” in France itself.
1794 — Robespierre is executed. France is governed by a Directory, a committee of five men.
1799 — Napoleon Bonaparte becomes the leader.
WOMEN’S REVOLUTION
From the very beginning, women were active participants in the events which brought about so many changes in the French society. Most women of the third estate had to work for a living.Their wages were lower than those of men. In order to discuss and voice their interests, women started their own political clubs and newspapers. One of their main demand was that women must enjoy the same political rights as men. Some laws were introduced to improve the position of women. Their struggle still continues in several parts of the world.It was finally in 1946 that women in France won the right to vote.
THE ABOLITION OF SLAVERY
There was a triangular slave trade between Europe, Africa and Americas. In the 18th century, there was little criticism of slavery in France. No laws were passed against it. It was in 1794 that the convention freed all slaves. But 10 years later slavery was reintroduced by Napoleon. It was finally in 1848 that slavery was abolished in the French colonies.
Why is photosynthesis considered an endothermic reaction?
In the photosynthesis process light energy from sunlight is absorbed to produce oxygen and glucose from carbon-dioxide and water in the presence of chlorophyll, and the process in which energy is absorbed is called as endothermic reaction, hence photosynthesis is a endothermic reaction.
On what basis is a chemical equation balanced?
A chemical equation is balanced on the basis of law of conservation of mass. According to this law mass can neither be created nor be destroyed.
List any four observations that help us to determine whether a chemical reaction has taken place ?
(i) Change in state
(ii) Change in colour
(iii) Evolution of a gas
(iv) Change in temperature.
What does symbol (aq) represent in a chemical equation?
The symbol (aq) represents aqueous solution. When it is written after a chemical formula in a chemical equation, it represents that the element or compound is a aqueous solution i.e water is added into the solution.
A magnesium ribbon should be cleaned before burning it in air. Why?
It should be cleaned to remove the dust particles and its oxides that may be present on its upper surface, so that it comes directly in contact with air.
State one difference between a physical change and a chemical change?
In a physical change, no new substance is formed while in a chemical change, a new substance is formed.
Is burning of a candle wax a physical change or a chemical change?
Chemical change(candle wax is a hydrocarbon,which burns to produce co2,soot etc.)
What is meant by a chemical reaction?
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another.
Example rusting of iron, burning of coal and digestion of food etc.
Describe the legacy of the French Revolution for the peoples of the world during the nineteenth and twentieth centuries.
Sol. The ideas of liberty and democratic rights were the most important legacy of the French Revolution. These spread from France to the rest of Europe during the nineteenth century, where feudal systems were abolished. Further these ideas spread to different colonies of the European nations. Colonised people interpreted and moulded these ideas according to respective needs. This was probably like seed for an end of colonization in many countries. By the mid of 20th century major part of the world adopted democracy as the preferred mode of rule and the French Revolution can be termed as the initiation point for this development.
Which groups of French society benefited from the revolution? Which groups were forced to relinquish power? Which sections of society would have been disappointed with the outcome of the revolution?
Sol. Peasants and artisans of French society benefited from the revolution. Clergy, nobles and church had to relinquish power. It is obvious that those who had to forego power and privileges would have been disappointed. People from the first and the second estate must have been a disappointed lot.
Describe the circumstances leading to the outbreak of revolutionary protest in France.
Sol. Following are some of the causes which had a cumulative effect to result in revolution in France:
(a) The war with Britain for an independent America: This war led to mounting debt on the
French monarchy. This necessitated imposition of new taxes on the public.
(b) Privilege based on birth: People got privileges and position based on their lineage and not on their merit. This led to resentment among common people.
(c) Concentration of power among the privileged: People belonging to the first and second estate had all the power and money. Masses were at the mercy of this privileged class (d) Subsistence Crisis:- Rising population and less grain production resulted in demand supply gap of bread, which was the staple diet. Wages did not keep pace with rising prices. It was becoming difficult for people.
(e) Growing Middle Class: Because of increased overseas trade a new class emerged. This class was wealthy not because of birth but because of its ability to utilize opportunities. People of the middle class started raising their voice for an end to privileges based on lineage.
All of this led to a general sense of resentment among people. Certain thinkers of the period spread awareness through various media. Some from the privileged classes also advocated a switch to democracy. So, finally there was revolution in France.
The Island groups of India
Sol. The Lakshadweep Islands are in the Arabian Sea. Its area is 32 sq km. The administrative headquarters of Lakshadweep is at Kavaratti island. This group of islands is rich in terms of biodiversity.
The Andaman and Nicobar Islands are bigger in size and has more number of islands. This group of islands can be divided into two groups. The Andaman is in the north and the Nicobar is in the south. These islands too have rich biodiversity.
The Central Highlands
Sol. The Central Highlands lies to the north of the Narmada river. It covers the major portion of the Malwa plateau. The rivers in this region flow from southwest to northeast; which indicates the slope of this region. It is wider in the west and narrower in the east. Bundelkhand and Baghelkhand mark the eastward extension of this plateau. The plateau further extends eastwards into the Chhotanagpur plateau.
Write short notes on the following: (i) The Indian Desert
Sol. The Indian desert lies towards the western margins of the Aravali Hills. This region gets scanty rainfall which is less than 150 mm in a year. Hence they climate is arid and vegetation is scanty. Luni is the only large river but some streams appear during rainy season. Crescent-shaped dunes (barchans) abound in this area.
Which are the major physiographical divisions of India? Contrast the relief of the Himalayan region with that of the Northern Plains of India.
Sol. The landmass of India can be divided into following major physiographic divisions:
(a) The Himalayan Mountains
(b) The Northern Plains
(c) The Peninsular Plateau
(d) The Indian Desert
(e) The Coastal Plains
(f) The Islands
The Himalayan region is rugged and shows great variations in terms altitude. The Northern Plains, on the other hand, is more or less level and has least variations in terms of altitude. The Himalayan region is formed by rocks and unconsolidated sediments. The Northern Plains is composed of alluvial deposits.
Describe how the Himalayas were formed.
Sol. The Indian Peninsula drifted towards the north and finally collided with the much larger Eurasian Plate. As a result of this collision, the sedimentary rocks which were accumulated in the geosynclines (known as Tethys) got folded and formed the mountain systems of the West Asia and Himalaya.
Bhangar and Khadar
Sol. Bhangar is the largest part of the Northern Plains and is formed by the oldest alluvium. On the other hand, Khadar is the younger deposit of alluvium.
Distinguish between (i) Converging and diverging tectonic plates
Sol. The converging tectonic plates move away from each other, while diverging plates move towards each other.
Name the island group of India having coral origin.
Sol. Lakshadweep
Which plateau lies between the Aravali and the Vindhyan ranges?
Sol. The Malwa plateau lies between the Aravali and the Vindhyan ranges.
Name the three major divisions of the Himalayas from north to south.
Sol. Three major division of the Himalayas from north to south are: (a) The Great or Inner Himalaya
(b) The Lesser Himalaya or Himachal
(c) The Shiwaliks
What is bhabar?
Sol. After descending from the mountains, the rivers deposit pebbles in a narrow belt. The width of this belt is about 8 to 16 km and it lies parallel to the Shiwaliks. This region is known as bhabar. All the streams disappear in this region.
Which continents of today were part of the Gondwana land?
Sol. The Malwa plateau lies between the Aravali and the Vindhyan ranges.
What are tectonic plates?
Sol. The crust of the earth is not in the form of a continuous plate rather in the form of broken pieces. These pieces of the earth’s crust are called tectonic plates.
The central location of India at the head of the Indian Ocean is considered of great significance. Why?
Sol. The trans Indian Ocean routes which connect the countries of Europe in the West and the countries of East Asia provide a strategic central location to India.
The sun rises two hours earlier in Arunachal Pradesh as compared to Gujarat in the west but the watches show the same time. How does this happen?
Sol. The latitudinal and longitudinal extent of the mainland is about 30°. Despite this fact, the east-west extent appears to be smaller than the north-south extent. From Gujarat to Arunachal Pradesh there is a time lag of two hours. Hence, time along the Standard Meridian of India (82°30'E) passing through Mirzapur (in Uttar Pradesh) is taken as the standard time for the whole country. The latitudinal extent influences the duration of the day and night, as one moves from south to north.
Which island group of India lies to its south-east?
Sol. (i) Lakshadweep islands.
(ii) Russia, Canada , USA, China, Brazil and Australia.
(iii) Andaman and Nicobar islands.
Name the countries which are larger then India.
Sol. Australia, Brazil, Canada, China, Russia and USA
Name the group of islands lying in the Arabian sea.
Sol. LAkshadweep
Define melting point and Boiling point ?
Melting point : It is the temperature at which a solid changes to liquid. Different Higher melting point means large force of attraction between particles.
Boiling point : It is the temperature at which a liquid changes to gas.
Define latent heat of Fusion, is it same as latent heat of vaporization ? Comment ?
Latent heat of fusion is the amount of heat required to convert 1 kg of solid at its melting point to liquid at same temperature.
Latent heat of vaporization It is the amount of heat required to convert 1 kg of liquid at its boiling point to gas at same temperature. Different liquid has different latent heat of vaporization.
No, Latent heat of fusion is not same as latent heat of vaporization.
What are the properties of gases ?
(i) Gases can be compressed easily
(ii) Gases neither have fixed shape nor fixed volume
(iii) Gases have very low densities
(iv) Gases have fluidity
(v) Particles of gases have very large spacing and very weak attraction between them.
Define the term inter - conversion of matter ?
The phenomenon of change of one state of matter into another an back to the original state is called inter - conversion of matter.
What is meant by physical property of substance ? Name the important physical property ?
Physical properties : Those properties of a substance which we can observed without altering the identity of the state.
- Colour
- Smell
-Density
- Solubicity
- Melting point and boiling point
- Conductivity
Define density and write down its S.I unit ?
Density means mass per unit volume
Density = mass / volume
Particles in solids are very closely packed so they have high density. In gases, there is plenty of spaces between particles due to which density is low.
S.I unit of density is kg/m3 (kilogram per cubic meter).
Why is oxygen called as gas ? Give two reasons ?
(i) Oxygen neither has a fixed shape nor a fixed volume.
(ii) Oxygen exerts pressure due to the collisions of the molecules on the walls of the containing vessel.
Give two reasons to justify - (a) Water at room temperature is a liquid (b) An Iron almirah is a solid at room temperature.
(a) Water is a liquid because of the following two reasons :
(i) liquids do not have a fixed shape : They take the shape of the container in which they are kept
(ii) Liquids have a fixed volume : Take 100 ml of water in a beaker. Transfer it to a glass, It still remains same, therefore, water is a liquid.
(b) An Iron almirah is a solid at room temperature due to following reasons :
(i) Iron almirah has a fixed shape and a fixed volume
(ii) If we apply force in limits, the volume of iron almirah cannot changed, hence it is in compressible, So it is a solid.
Rearrange the following substance in increasing order of forces of attraction between the particles ? Oxygen , Water & Sugar ?
The forces of attraction are the strongest in solids, followed by liquids and weakest in gases
Solids > liquids ? gases
Therefore, the force of attraction between particles increases in the order
Oxygen < Water < Sugar
Comment upon the following : Rigidity, Compressibility, fluidity, Density, shape and volume
Compressibility : It means tendency to decrease volume when some outside force is applied. Spacing between particles of gases can be decreased so gases have high compressibility. But spacing between particles of solid or liquid can not be decreased, so they cannot be compressed.
Applications of compressed Gas -
- Compressed helium gas is filled in air balloons.
- Compressed natural gas (CNG) is filled in cylinders which are used for cooking.
Rigidity - It is the property of a substance to resist any deformation like change in shape, being compressed etc. Solids have high rigidity, liquids have less rigidity and gases have no rigidity.
Fluidity
- Fluids are substances which can flow
- Liquids and gases have fluidity
- But solids do not have fluidity
Density : It means mass per unit volume
Density = Mass / Volume
Particles in solids are very closely packed So they have high density. In gases, there is plaenty of space between particles due to which density is low.
Shape and volume
Shape - Due to less attraction force between particles, particles of liquid and gas can easily move around. This they can take any shape as per the container.
Volume -
- gases have so little attraction among particles that they can easily change spacing between them selves, So they can easily change their volume.
- In liquids, attraction force is large enough So that spacing between particles does not change easily, So liquid has fireed volume and same with solids.
- Solids can change shape on applying force Liquids and gases do not need force to be applied for changing shape.
- Some solids have gas inside them, So they can be easily squeezed to change shope.
Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why ?
Ice has cage like structure, i.e, when water freezes to form ice, a number of empty spaces are created. As a result, volume increases for the same mass of water. of we can say that density of ice is lower than that of water an hence ice floats over water.
Write down three application of compressed gas ?
(i) Compressed helium gas is filled in air balloons
(ii) Compressed natural gas (CNG) is filled in cylinders which are used in vehicles.
(iii) Liquefied petroleum gas (LPG) is filled in cylinders which are used for cooking.
Name the two gases which are supplied in compressed form ?
The two gases which are supplied in compressed form are.
(i) LPG (Liquefied petroleum gas ) in homes
(ii) Oxygen in hospitals
How will you justify that ice, water and steam are the three states of a substance and not different substances ?
When ice is melted, water is produced and when water is heated steam is produced on the other hand, when water is cooled further, ice is produced. Therefore ice, water and steam are the three states of a substance.
Out of solids, liquids and gases, which one has . (a) Maximum movement of particles (b) Maximum inter particle forces of attraction . (c) Minimum spaces in between constituent particles.
(a) Because of large spaces between the particles of a gas, gases have maximum movement of particles.
(b) and (c) In Solids, the spaces between the constituent particles are the minimum and hence the forces of attraction are the strongest.
Out of dry and wet air which is heavier ?
Since water vapours are heavier than air, therefore, wet air is heavier than dry air.
How do solids, liquids and gases differ in shape and volume ?
Solids have a definite shape and a fixed volume, liquids have a definite volume but no fixed shape while gases neither have a definite volume nor a definite shape.
Name the physical state of matter which can be easily compressed ?
Gas : Gas is highly compressible
Define solid, liquid and gas with example ?
Solid : Solids have fireed volume and shape in solids. In solids, particles are closely packed and they have very less spacing between them
Examples : stone, wood, brick etc .
Liquid : Liquids have fixed volume but indefinite shape. In liquids there is a weaker force of attraction and more spacing between the particles
Examples : milk, water, petrol etc.
Gas : Gases have indefinite shape and volume particles of gases have very large spacing and very weak attraction between them
Examples : air, oxygen, hydrogen etc
Which term is used to describe the mixing of copper sulphate with water in a breaker on its own ?
Diffusion is used to describe the mixing of copper sulphate with water in a beaker on its own.
What is diffusion ?
The process of mixing of two substances due to Brownian motion of particles is called diffusion. As temperature increases, Brownian motion increases and diffusion becomes fast. Diffusion takes place from higher concentration to lower concentration. It is a natural process. It takes palace in solid, liquid and gases.
What provides the best evidence about the random motion of particles in matter ?
Diffusion and Brownian motion, provide the best evidence about the random motion of particles in matter.
A diver is able to cut through water in a swimming pool. Which property of matter does this observation show ?
The ability of a diver to cut through water in a swimming pool shows that matter is made up of particles.
List the important properties of matter ?
Properties of matter :
- Matter is made up of small particles
- These particles are very small in size
- These particles are moving constantly
- These particles have spaces between them
- Particles of matter attract each other because of force of attraction.
Q.3 A substance has a definite shape as well as definite volume. Which physical state is represented by this statement ?
Solids have a definite shape as well as a definite volume.
What is matter ?
Anything which occupies space and has mass is called matter. In other words, anything which has mass and volume is called matter.
For example : chair, table, computer, mouse etc.
Name the three common states of matter. Give one example of each ?
Solid (ice), liquid (water), gas (oxygen)
Class 10th Science Solution: Chapter 10 Light-Reflection and refraction
Question 1:
Which one of the following materials cannot be used to make a lens?
Water
Glass
Plastic
Clay
Answer 1:
(d) A lens allows light to pass through it. Since clay does not show such property, it cannot be used to make a lens.
Question 2:
The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?
Between the principal focus and the centre of curvature
At the centre of curvature
Beyond the centre of curvature
Between the pole of the mirror and its principal focus.
Answer 2:
(d) When an object is placed between the pole and principal focus of a concave mirror, the image formed is virtual, erect, and larger than the object.
Question 3:
Where should an object be placed in front of a convex lens to get a real image of the size of the object?
At the principal focus of the lens
At twice the focal length
At infinity
Between the optical centre of the lens and its principal focus.
Answer 3:
(b) When an object is placed at the centre of curvature in front of a convex lens, its image is formed at the centre of curvature on the other side of the lens. The image formed is real, inverted, and of the same size as the object.
Question 4:
A spherical mirror and a thin spherical lens have each a focal length of −15 cm. The mirror and the lens are likely to be
both concave
both convex
the mirror is concave and the lens is convex
the mirror is convex, but the lens is concave
Answer 4:
By convention, the focal length of a concave mirror and a concave lens are taken as negative. Hence, both the spherical mirror and the thin spherical lens are concave in nature.
Question 5:
No matter how far you stand from a mirror, your image appears erect. The mirror is likely to be
plane
concave
convex
either plane or convex
Answer 5:
(d) A convex mirror always gives a virtual and erect image of smaller size of the object placed in front of it. Similarly, a plane mirror will always give a virtual and erect image of same size as that of the object placed in front of it. Therefore, the given mirror could be either plane or convex.
Question 6:
Which of the following lenses would you prefer to use while reading small letters found in a dictionary?
A convex lens of focal length 50 cm
A concave lens of focal length 50 cm
A convex lens of focal length 5 cm (d) A concave lens of focal length 5 cm
Answer 6:
(c) A convex lens gives a magnified image of an object when it is placed between the radius of curvature and focal length. Also, magnification is more for convex lenses having shorter focal length. Therefore, for reading small letters, a convex lens of focal length 5 cm should be used.
Question 7:
We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.
Answer 7:
Range of object distance = 0 cm to15 cm
A concave mirror gives an erect image when an object is placed between its pole (P) and the principal focus (F).
Hence, to obtain an erect image of an object from a concave mirror of focal length 15 cm, the object must be placed anywhere between the pole and the focus. The image formed will be virtual, erect, and magnified in nature, as shown in the given figure.
Question 8:
Name the type of mirror used in the following situations.
Headlights of a car
Side/rear-view mirror of a vehicle
Solar furnace
Support your answer with reason.
Answer 8:
Concave
Convex
Concave
Explanation
Concave mirror is used in the headlights of a car. This is because concave mirrors can produce powerful parallel beam of light when the light source is placed at their principal focus.
Convex mirror is used in side/rear view mirror of a vehicle. Convex mirrors give a virtual, erect, and diminished image of the objects placed in front of it. Because of this, they have a wide field of view. It enables the driver to see most of the traffic behind him/her.
Concave mirrors are convergent mirrors. That is why they are used to construct solar furnaces. Concave mirrors converge the light incident on them at a single point known as principal focus. Hence, they can be used to produce a large amount of heat at that point.
Question 9:
One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.
Answer 9:
The convex lens will form complete image of an object, even if its one half is covered with black paper. It can be understood by the following two cases.
Case I
When the upper half of the lens is covered
In this case, a ray of light coming from the object will be refracted by the lower half of the lens. These rays meet at the other side of the lens to form the image of the given object, as shown in the following figure.
Case II
When the lower half of the lens is covered
In this case, a ray of light coming from the object is refracted by the upper half of the lens. These rays meet at the other side of the lens to form the image of the given object, as shown in the following figure.
Question 10:
An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.
Answer 10:
Object distance, u = −25 cm
Object height, ho = 5 cm
Focal length, f = +10 cm
The negative value of image height indicates that the image formed is inverted. The position, size, and nature of image are shown in the following ray diagram.
Question 11:
A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram.
Answer 11:
Focal length of concave lens (OF1), f = −15 cm
Image distance, v = −10 cm
According to the lens formula,
The negative value of u indicates that the object is placed 30 cm in front of the lens. This is shown in the following ray diagram.
Question 12:
An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.
Answer 12:
Focal length of convex mirror, f = +15 cm Object distance, u = −10 cm
Question 13:
The magnification produced by a plane mirror is +1. What does this mean?
Answer 13:
Magnification produced by a mirror is given by the relation
The magnification produced by a plane mirror is +1. It shows that the image formed by the plane mirror is of the same size as that of the object. The positive sign shows that the image formed is virtual and erect.
Question 14:
An object 5.0 cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position of the image, its nature and size.
Answer 14:
Object distance, u = −20 cm
Object height, h = 5 cm
Radius of curvature, R = 30 cm
Radius of curvature = 2 × Focal length
R = 2f f = 15 cm
Therefore, the image formed is virtual, erect, and smaller in size.
Question 15:
An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focused image can be obtained? Find the size and the nature of the image.
Answer 15:
Object distance, u = −27 cm
Object height, h = 7 cm
Focal length, f = −18 cm
The negative value of image height indicates that the image formed is inverted.
Question 16:
Find the focal length of a lens of power −2.0 D. What type of lens is this?
A concave lens has a negative focal length. Hence, it is a concave lens.
Question 17:
A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?
A convex lens has a positive focal length. Hence, it is a convex lens or a converging lens.
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