SECTION A – Biology
Question 1: Identify the part that controls the closing and opening of the stomatal pore in leaves of plants. [1] Select the correct option. [1]
Answer: (C) Guard cells
Question 2: Identify the endocrine gland that regulates the growth of human body. [1]
Answer: (A) Pituitary gland
Question 3: Choose the equation of reaction that correctly represents anaerobic respiration in muscles: [1]
Answer: (D) Glucose \(\rightarrow\) Pyruvate \(\xrightarrow{\text{Lack of oxygen}}\) Lactic acid + Energy
Question 4: In human beings, the implantation of fertilised egg takes place in which part of female reproductive system? [1]
Answer: (C) Uterus
Question 5: When a human egg is fertilized by a sperm having 'Y' chromosome, the zygote has the following combination of chromosomes: [2]
Answer: (C) 44 + XY
Question 6: Which of the following is a non-biodegradable pollutant? [2]
Answer: (B) DDT
Question 7: In an ecosystem, the decomposers perform an important role. [2] Select the option indicating the role of decomposers. [2]
Answer: (B) Break down complex organic substances to simple inorganic substances.
Question 8: Assertion (A) : Bacteria that can withstand heat have better chances of survival in a heat wave. [3]
Reason (R) : Accumulation of variations in a species increases the chances of its survival in changing environment. [3]
Reason (R) : Accumulation of variations in a species increases the chances of its survival in changing environment. [3]
Answer: (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
Question 9: Assertion (A) : The peristaltic movements occur all along the gut. [3]
Reason (R) : The lining of the gut has muscles that contract rhythmically to push the food in regulated manner. [3]
Reason (R) : The lining of the gut has muscles that contract rhythmically to push the food in regulated manner. [3]
Answer: (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
Question 10: Give a diagrammatic representation of nutrition in Amoeba. [3]
Answer: (Diagrammatic response required) The diagram should illustrate the five stages of holozoic nutrition in Amoeba:
1. Ingestion (formation of pseudopodia around the food particle),
2. Digestion (formation of food vacuole),
3. Absorption,
4. Assimilation, and
5. Egestion.
1. Ingestion (formation of pseudopodia around the food particle),
2. Digestion (formation of food vacuole),
3. Absorption,
4. Assimilation, and
5. Egestion.
Question 11:
(A) Observe the given figure and identify the labelled parts P, Q, R and S : [3] OR
(B) Which of the plant hormones are responsible for the following processes? [4]
(i) Promote cell division [4]
(ii) Inhibition of growth [4]
(iii) Detection of light [4]
(iv) Wilting of leaves [4]
(B) Which of the plant hormones are responsible for the following processes? [4]
(i) Promote cell division [4]
(ii) Inhibition of growth [4]
(iii) Detection of light [4]
(iv) Wilting of leaves [4]
Answer:
(A) In the reflex arc: P = Receptor (e.g., skin), Q = Sensory neuron, R = Motor neuron, S = Effector (muscle).
OR
(B) (i) Cytokinins, (ii) Abscisic acid, (iii) Auxins, (iv) Abscisic acid.
(A) In the reflex arc: P = Receptor (e.g., skin), Q = Sensory neuron, R = Motor neuron, S = Effector (muscle).
OR
(B) (i) Cytokinins, (ii) Abscisic acid, (iii) Auxins, (iv) Abscisic acid.
Question 12: Briefly mention the steps in double-circulation through human heart. [4]
Answer: Double circulation involves two distinct pathways:
1. Pulmonary Circulation: Deoxygenated blood is pumped from the right ventricle to the lungs for oxygenation and returns as oxygenated blood to the left atrium.
2. Systemic Circulation: Oxygenated blood is pumped from the left ventricle to all body parts and returns as deoxygenated blood to the right atrium.
1. Pulmonary Circulation: Deoxygenated blood is pumped from the right ventricle to the lungs for oxygenation and returns as oxygenated blood to the left atrium.
2. Systemic Circulation: Oxygenated blood is pumped from the left ventricle to all body parts and returns as deoxygenated blood to the right atrium.
Question 13: Based on Mendel's experiment show the cross between round, yellow seeds of pea plant (RRYY) with wrinkled and green seeds of pea plant (rryy) upto \(F_2\) generation. [4] Write the number of seeds/plants with following genetic (Genotype) makeup in \(F_2\) generation: [4]
(i) RRYY [4]
(ii) rryy [4]
(i) RRYY [4]
(ii) rryy [4]
Answer: The \(F_1\) generation produces all heterozygous round yellow seeds (RrYy). When \(F_1\) is self-pollinated, it results in an \(F_2\) generation phenotypic ratio of 9:3:3:1. Out of a total of 16 possible combinations:
(i) The number of RRYY genotype = 1
(ii) The number of rryy genotype = 1.
(i) The number of RRYY genotype = 1
(ii) The number of rryy genotype = 1.
Question 14:
(a) Mention any one harmful effect of using plastic bags on the environment. [4] Suggest better alternatives to the usage of plastic bags. [4]
(b) Paddy fields require a large amount of water. [4] The pesticides and chemical fertilizers used are washed down into the soil or waterbodies. [4] How do these chemicals reach our bodies? [4] What is this phenomenon known as? [4]
(b) Paddy fields require a large amount of water. [4] The pesticides and chemical fertilizers used are washed down into the soil or waterbodies. [4] How do these chemicals reach our bodies? [4] What is this phenomenon known as? [4]
Answer:
(a) Plastic bags are non-biodegradable and can clog drains or be fatal to animals if ingested. Alternatives: Jute bags, cloth bags, or paper bags.
(b) Chemicals from soil and water are absorbed by plants, which are then consumed by animals and humans, moving up the food chain. This phenomenon of progressive accumulation of chemicals at each trophic level is known as Biological Magnification (or Biomagnification).
(a) Plastic bags are non-biodegradable and can clog drains or be fatal to animals if ingested. Alternatives: Jute bags, cloth bags, or paper bags.
(b) Chemicals from soil and water are absorbed by plants, which are then consumed by animals and humans, moving up the food chain. This phenomenon of progressive accumulation of chemicals at each trophic level is known as Biological Magnification (or Biomagnification).
Question 15: Kidneys help to regulate the volume of fluid and various metabolites waste products in the body. [4] Normally, kidney filter about 180 L of fluid daily but the volume actually excreted out is only a litre or two a day. [4] Patients with kidney failures can be saved by dialysis and kidney transplant. [5]
(a) Write the structure and function of Bowman's capsule. [5]
(b) Although kidneys filter a large amount (about 180 L daily) of fluids, still the excretion from the body is only about a litre or two. [5] Why? [5]
(c) What is excretion? [5] Why is it necessary for any living organism? [5] OR
(c) State two similarities between lungs and kidneys. [5]
(b) Although kidneys filter a large amount (about 180 L daily) of fluids, still the excretion from the body is only about a litre or two. [5] Why? [5]
(c) What is excretion? [5] Why is it necessary for any living organism? [5] OR
(c) State two similarities between lungs and kidneys. [5]
Answer:
(a) Bowman's capsule is a cup-shaped, double-walled structure at the beginning of a nephron. It encloses the glomerulus and functions to filter blood to form primary urine (ultrafiltration).
(b) Most of the filtered volume is reabsorbed (water, glucose, amino acids) by the tubular part of the nephron back into the blood, leaving only a small amount of concentrated urine to be excreted.
(c) Excretion is the biological process of removing harmful metabolic wastes from the body. It is necessary to prevent the toxic buildup of these wastes, which can disrupt homeostasis and cause death.
OR
(c) Similarities: Both are excretory organs (lungs excrete \(CO_2\), kidneys excrete nitrogenous wastes), and both have a very large surface area supplied with an extensive network of blood capillaries for exchange/filtration.
(a) Bowman's capsule is a cup-shaped, double-walled structure at the beginning of a nephron. It encloses the glomerulus and functions to filter blood to form primary urine (ultrafiltration).
(b) Most of the filtered volume is reabsorbed (water, glucose, amino acids) by the tubular part of the nephron back into the blood, leaving only a small amount of concentrated urine to be excreted.
(c) Excretion is the biological process of removing harmful metabolic wastes from the body. It is necessary to prevent the toxic buildup of these wastes, which can disrupt homeostasis and cause death.
OR
(c) Similarities: Both are excretory organs (lungs excrete \(CO_2\), kidneys excrete nitrogenous wastes), and both have a very large surface area supplied with an extensive network of blood capillaries for exchange/filtration.
Question 16:
(A) (i) In an angiospermic flower, fertilization is said to take place when male gametes carried in the pollen tube fuse with the female gamete, present in the embryo sac. [5] This results in lot of changes in different parts of the flower. [5] State the changes taking place in the following structures of flower post fertilization: (a) Zygote (b) Ovule (c) Ovary (d) Sepals [5]
(ii) Define germination. [5]
OR
(B) (i) Sugarcane does not produce seeds so name the process through which it will be able to reproduce. [5]
(ii) List any two advantages of this method. [5]
(iii) Besides sugarcane, give two more examples of plants that reproduce by this method. [5]
(iv) Why regeneration is not possible in all the types of animals? [5]
(ii) Define germination. [5]
OR
(B) (i) Sugarcane does not produce seeds so name the process through which it will be able to reproduce. [5]
(ii) List any two advantages of this method. [5]
(iii) Besides sugarcane, give two more examples of plants that reproduce by this method. [5]
(iv) Why regeneration is not possible in all the types of animals? [5]
Answer:
(A) (i) (a) Zygote develops into an embryo. (b) Ovule develops into a seed. (c) Ovary ripens into a fruit. (d) Sepals generally wither and fall off. (ii) Germination is the process by which an embryo within a seed becomes active and grows into a seedling under favorable conditions.
OR
(B) (i) Vegetative Propagation. (ii) Advantages: Plants grow faster and bear fruit earlier than those grown from seeds; the new plants are genetically identical to the parent plant. (iii) Potato, Rose. (iv) Regeneration requires specialized totipotent cells capable of multiplying and differentiating into various tissue types. Most higher animals have highly complex and specialized body designs that lack these cells in sufficient quantities.
(A) (i) (a) Zygote develops into an embryo. (b) Ovule develops into a seed. (c) Ovary ripens into a fruit. (d) Sepals generally wither and fall off. (ii) Germination is the process by which an embryo within a seed becomes active and grows into a seedling under favorable conditions.
OR
(B) (i) Vegetative Propagation. (ii) Advantages: Plants grow faster and bear fruit earlier than those grown from seeds; the new plants are genetically identical to the parent plant. (iii) Potato, Rose. (iv) Regeneration requires specialized totipotent cells capable of multiplying and differentiating into various tissue types. Most higher animals have highly complex and specialized body designs that lack these cells in sufficient quantities.
SECTION B – Chemistry
Question 17: The volume ratio of hydrogen and oxygen gases liberated during electrolysis of water is: [6]
Answer: (B) 2:1
Question 18: Which of the following set of compounds does not belong to same homologous series? [6]
Answer: (D) \(C_4H_8\) and \(C_5H_{12}\)
Question 19: Which of the following is an amphoteric oxide? [6]
Answer: (D) \(Al_2O_3\)
Question 20: Study the following table and select the correct option: [7]
Answer: (D) Salt: \(CH_3COONa\), Acid used: \(CH_3COOH\), Base used: \(NaOH\), Nature of Salt: Basic
Question 21: Which of the following will not undergo addition reaction? [7]
Answer: (C) \(C_3H_8\) (It is an alkane/saturated hydrocarbon)
Question 22: Four solutions, namely fructose, ethanol, hydrochloric acid and sodium hydroxide filled in four separate beakers are connected one by one in an electric circuit with a bulb. [7] The solutions in which the bulb will glow when current is passed are: [7]
Answer: (D) hydrochloric acid and sodium hydroxide
Question 23: Which gas is evolved when magnesium metal reacts with very dilute \(HNO_3\)? [7]
Answer: (C) Hydrogen
Question 24: Assertion (A) : Reaction of quick lime with water is an exothermic reaction. [8]
Reason (R) : A large amount of heat is evolved on the reaction of quick lime and water. [8]
Reason (R) : A large amount of heat is evolved on the reaction of quick lime and water. [8]
Answer: (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
Question 25: Define the following terms: [8]
(i) Olfactory indicator [8]
(ii) Water of crystallization [8]
(i) Olfactory indicator [8]
(ii) Water of crystallization [8]
Answer:
(i) Olfactory indicators are substances whose odor changes in acidic or basic media (e.g., vanilla extract or clove oil).
(ii) Water of crystallization is the fixed number of water molecules chemically attached to one formula unit of a salt in its crystalline form.
(i) Olfactory indicators are substances whose odor changes in acidic or basic media (e.g., vanilla extract or clove oil).
(ii) Water of crystallization is the fixed number of water molecules chemically attached to one formula unit of a salt in its crystalline form.
Question 26: What happens when [8]
(i) lead (II) nitrate is heated? [8]
(ii) iron (II) sulphate is heated? [8]
(iii) silver chloride is exposed to sunlight? [8]
Write balanced chemical equations of the reactions involved in support of your answer. [8]
(i) lead (II) nitrate is heated? [8]
(ii) iron (II) sulphate is heated? [8]
(iii) silver chloride is exposed to sunlight? [8]
Write balanced chemical equations of the reactions involved in support of your answer. [8]
Answer:
(i) Brown fumes of nitrogen dioxide gas are evolved and a yellow residue of lead oxide is left behind.
\(2Pb(NO_3)_2(s) \xrightarrow{\Delta} 2PbO(s) + 4NO_2(g) + O_2(g)\)
(ii) The green crystals change to a white residue initially, and then decompose to leave a brown solid (ferric oxide) with the smell of burning sulfur.
\(2FeSO_4(s) \xrightarrow{\Delta} Fe_2O_3(s) + SO_2(g) + SO_3(g)\)
(iii) White silver chloride turns grey due to its decomposition into silver metal and chlorine gas.
\(2AgCl(s) \xrightarrow{\text{Sunlight}} 2Ag(s) + Cl_2(g)\)
(i) Brown fumes of nitrogen dioxide gas are evolved and a yellow residue of lead oxide is left behind.
\(2Pb(NO_3)_2(s) \xrightarrow{\Delta} 2PbO(s) + 4NO_2(g) + O_2(g)\)
(ii) The green crystals change to a white residue initially, and then decompose to leave a brown solid (ferric oxide) with the smell of burning sulfur.
\(2FeSO_4(s) \xrightarrow{\Delta} Fe_2O_3(s) + SO_2(g) + SO_3(g)\)
(iii) White silver chloride turns grey due to its decomposition into silver metal and chlorine gas.
\(2AgCl(s) \xrightarrow{\text{Sunlight}} 2Ag(s) + Cl_2(g)\)
Question 27:
(A) (a) Give the chemical name and formula of Plaster of Paris. [9]
(b) Write the chemical equation of its preparation. [9]
(c) Give any two uses of it. [9]
OR
(B) (a) Name the acid present in ant's sting. [9]
(b) Give reason: (i) While diluting an acid, it is recommended that the acid should be added to water. [9] (ii) Baking soda is used as an antacid. [9]
(b) Write the chemical equation of its preparation. [9]
(c) Give any two uses of it. [9]
OR
(B) (a) Name the acid present in ant's sting. [9]
(b) Give reason: (i) While diluting an acid, it is recommended that the acid should be added to water. [9] (ii) Baking soda is used as an antacid. [9]
Answer:
(A) (a) Calcium sulphate hemihydrate, \(CaSO_4 \cdot \frac{1}{2}H_2O\).
(b) \(CaSO_4 \cdot 2H_2O \xrightarrow{373\text{ K}} CaSO_4 \cdot \frac{1}{2}H_2O + 1\frac{1}{2}H_2O\)
(c) Uses: 1. Making casts for fractured bones. 2. Making toys or decorative ceilings.
OR
(B) (a) Methanoic acid (Formic acid).
(b) (i) Diluting an acid is highly exothermic. Adding water to concentrated acid can cause sudden boiling and splashing, leading to severe acid burns. (ii) Baking soda is a mild, non-corrosive base that neutralizes the excess acid in the stomach to relieve indigestion.
(A) (a) Calcium sulphate hemihydrate, \(CaSO_4 \cdot \frac{1}{2}H_2O\).
(b) \(CaSO_4 \cdot 2H_2O \xrightarrow{373\text{ K}} CaSO_4 \cdot \frac{1}{2}H_2O + 1\frac{1}{2}H_2O\)
(c) Uses: 1. Making casts for fractured bones. 2. Making toys or decorative ceilings.
OR
(B) (a) Methanoic acid (Formic acid).
(b) (i) Diluting an acid is highly exothermic. Adding water to concentrated acid can cause sudden boiling and splashing, leading to severe acid burns. (ii) Baking soda is a mild, non-corrosive base that neutralizes the excess acid in the stomach to relieve indigestion.
Question 28: Alcohol forms a homologous series with general formula \(C_nH_{2n+1}-OH\) and -OH group as functional group. [9] Ethanol is commonly called alcohol and is used in alcoholic drinks. [9] It is good solvent, used in medicines, cough syrups, tonics etc. [9]
(a) Write structural formula and name of 4th member of alcohol homologous series. [9]
(b) What happens when ethanol is heated with alkaline \(KMnO_4\)? [9] Write chemical equation involved. [9]
(c) Write the chemical equation of reaction of ethanol with ethanoic acid in the presence of concentrated \(H_2SO_4\). [9] Write the name of this reaction. [9] OR
(c) What happens when ethanol is heated with excess concentrated sulphuric acid at 443 K? [9] Write chemical equation involved. [9] What is the role of concentrated sulphuric acid in this reaction? [9]
(b) What happens when ethanol is heated with alkaline \(KMnO_4\)? [9] Write chemical equation involved. [9]
(c) Write the chemical equation of reaction of ethanol with ethanoic acid in the presence of concentrated \(H_2SO_4\). [9] Write the name of this reaction. [9] OR
(c) What happens when ethanol is heated with excess concentrated sulphuric acid at 443 K? [9] Write chemical equation involved. [9] What is the role of concentrated sulphuric acid in this reaction? [9]
Answer:
(a) 4th member is Butanol. Formula: \(C_4H_9OH\) (or \(CH_3-CH_2-CH_2-CH_2-OH\)).
(b) It is oxidized to ethanoic acid.
\(CH_3CH_2OH \xrightarrow{\text{Alk. } KMnO_4 + \Delta} CH_3COOH + H_2O\)
(c) A sweet-smelling ester (ethyl ethanoate) is formed. This reaction is called Esterification.
\(CH_3COOH + C_2H_5OH \xrightarrow{\text{Conc. } H_2SO_4} CH_3COOC_2H_5 + H_2O\)
OR
(c) It undergoes dehydration to form ethene.
\(CH_3CH_2OH \xrightarrow{\text{Conc. } H_2SO_4, 443\text{K}} CH_2=CH_2 + H_2O\).
Concentrated sulphuric acid acts as a dehydrating agent.
(a) 4th member is Butanol. Formula: \(C_4H_9OH\) (or \(CH_3-CH_2-CH_2-CH_2-OH\)).
(b) It is oxidized to ethanoic acid.
\(CH_3CH_2OH \xrightarrow{\text{Alk. } KMnO_4 + \Delta} CH_3COOH + H_2O\)
(c) A sweet-smelling ester (ethyl ethanoate) is formed. This reaction is called Esterification.
\(CH_3COOH + C_2H_5OH \xrightarrow{\text{Conc. } H_2SO_4} CH_3COOC_2H_5 + H_2O\)
OR
(c) It undergoes dehydration to form ethene.
\(CH_3CH_2OH \xrightarrow{\text{Conc. } H_2SO_4, 443\text{K}} CH_2=CH_2 + H_2O\).
Concentrated sulphuric acid acts as a dehydrating agent.
Question 29: Attempt either option (A) or (B): [10]
(A) (i) Give reasons for the following: [10] (I) Ionic compound have generally high melting points and boiling points. [10] (II) Solder, an alloy of lead and tin, is used for welding electrical wires. [10] (III) Carbon cannot reduce the oxides of Na or Mg. [10]
(ii) The reaction of compound 'X' with aluminium is used to join railway tracks: [10] (I) Identify the compound 'X'. [10] (II) Name the reaction. [10] (III) Write the balanced chemical equation of the reaction of compound 'X' with aluminium. [10]
OR
(B) (i) Write the balanced chemical equations when: [10] (I) A mixture of \(Cu_2O\) and \(Cu_2S\) is heated. [10] (II) ZnS is heated in the presence of oxygen. [10]
(ii) Give reasons for the following: [10] (I) The wires carrying current in homes have a coating of PVC. [10] (II) To make hot water tanks, copper is used and not steel. [10]
(iii) Show the formation of ionic compound CaO with electron dot structure. [10] [Atomic number : Ca = 20, O = 8] [10]
(ii) The reaction of compound 'X' with aluminium is used to join railway tracks: [10] (I) Identify the compound 'X'. [10] (II) Name the reaction. [10] (III) Write the balanced chemical equation of the reaction of compound 'X' with aluminium. [10]
OR
(B) (i) Write the balanced chemical equations when: [10] (I) A mixture of \(Cu_2O\) and \(Cu_2S\) is heated. [10] (II) ZnS is heated in the presence of oxygen. [10]
(ii) Give reasons for the following: [10] (I) The wires carrying current in homes have a coating of PVC. [10] (II) To make hot water tanks, copper is used and not steel. [10]
(iii) Show the formation of ionic compound CaO with electron dot structure. [10] [Atomic number : Ca = 20, O = 8] [10]
Answer:
(A) (i) (I) Due to strong electrostatic forces of attraction between oppositely charged ions, a large amount of energy is required to break these bonds. (II) It has a low melting point. (III) Na and Mg are highly reactive metals and have a stronger affinity for oxygen than carbon does.
(ii) (I) X is Iron(III) oxide (\(Fe_2O_3\)). (II) Thermite reaction. (III) \(Fe_2O_3(s) + 2Al(s) \rightarrow 2Fe(l) + Al_2O_3(s) + \text{Heat}\).
OR
(B) (i) (I) \(2Cu_2O + Cu_2S \xrightarrow{\Delta} 6Cu + SO_2\)
(II) \(2ZnS + 3O_2 \xrightarrow{\Delta} 2ZnO + 2SO_2\)
(ii) (I) PVC is an electrical insulator and prevents electric shocks. (II) Copper is a better conductor of heat than steel and does not react with cold/hot water or steam, whereas steel (iron) can rust by reacting with steam.
(iii) Electron dot structure:
Ca (2,8,8,2) \(\rightarrow\) \(Ca^{2+} + 2e^-\)
O (2,6) + \(2e^-\) \(\rightarrow\) \(O^{2-}\)
The two valence electrons of Ca are transferred to the O atom to form the ionic compound \(Ca^{2+}[ : \ddot{O} : ]^{2-}\).
(A) (i) (I) Due to strong electrostatic forces of attraction between oppositely charged ions, a large amount of energy is required to break these bonds. (II) It has a low melting point. (III) Na and Mg are highly reactive metals and have a stronger affinity for oxygen than carbon does.
(ii) (I) X is Iron(III) oxide (\(Fe_2O_3\)). (II) Thermite reaction. (III) \(Fe_2O_3(s) + 2Al(s) \rightarrow 2Fe(l) + Al_2O_3(s) + \text{Heat}\).
OR
(B) (i) (I) \(2Cu_2O + Cu_2S \xrightarrow{\Delta} 6Cu + SO_2\)
(II) \(2ZnS + 3O_2 \xrightarrow{\Delta} 2ZnO + 2SO_2\)
(ii) (I) PVC is an electrical insulator and prevents electric shocks. (II) Copper is a better conductor of heat than steel and does not react with cold/hot water or steam, whereas steel (iron) can rust by reacting with steam.
(iii) Electron dot structure:
Ca (2,8,8,2) \(\rightarrow\) \(Ca^{2+} + 2e^-\)
O (2,6) + \(2e^-\) \(\rightarrow\) \(O^{2-}\)
The two valence electrons of Ca are transferred to the O atom to form the ionic compound \(Ca^{2+}[ : \ddot{O} : ]^{2-}\).
SECTION C – Physics
Question 30: Rays from the sun converge at a point 25 cm behind a convex lens. [11] The distance at which an object be placed in front of the lens to get a virtual image, is: [11]
Answer: (A) 20 cm (Since focal length f = +25 cm, to get a virtual image, the object must be placed within the focal length, i.e., distance < 25 cm).
Question 31: To restore clear vision in persons whose size of the eye ball has reduced, he/she is suggested to use suitable: [11]
Answer: (A) Converging lens (A reduced eyeball causes hypermetropia, which is corrected with a convex/converging lens).
Question 32: Assertion (A) : The needle of a magnetic compass kept in strong external magnetic field, always aligns itself in north-south direction on the earth. [11]
Reason (R) : Behaviour of the needle of a compass is same as that of a freely suspended bar magnet. [11]
Reason (R) : Behaviour of the needle of a compass is same as that of a freely suspended bar magnet. [11]
Answer: (D) Assertion (A) is false, but Reason (R) is true. (In a strong external field, the needle will align with the external field, not necessarily N-S).
Question 33:
(a) Relate the speed of light in the given medium with its optical density. [11]
(b) Using the information given in the table below, arrange the medium A, B and C in the ascending order of their optical density. [11]
Medium A: \(2.25 \times 10^8\) m/s [11]
Medium B: \(2 \times 10^8\) m/s [11]
Medium C: \(2.08 \times 10^8\) m/s [11]
(b) Using the information given in the table below, arrange the medium A, B and C in the ascending order of their optical density. [11]
Medium A: \(2.25 \times 10^8\) m/s [11]
Medium B: \(2 \times 10^8\) m/s [11]
Medium C: \(2.08 \times 10^8\) m/s [11]
Answer:
(a) The speed of light in a medium is inversely proportional to its optical density.
(b) Ascending order of optical density means descending order of speed of light.
Speed order: A (\(2.25 \times 10^8\)) > C (\(2.08 \times 10^8\)) > B (\(2 \times 10^8\)).
Therefore, optical density order: A < C < B.
(a) The speed of light in a medium is inversely proportional to its optical density.
(b) Ascending order of optical density means descending order of speed of light.
Speed order: A (\(2.25 \times 10^8\)) > C (\(2.08 \times 10^8\)) > B (\(2 \times 10^8\)).
Therefore, optical density order: A < C < B.
Question 34:
(A) (i) How does the change in curvature of the eye lens helps us in the process of seeing the nearby objects clearly? [12] (ii) State the range of the power of accommodation of a normal human eye. [12]
OR
(B) Draw a ray diagram to show the correction of eye defect of an old man who can not see an object placed closer than 1 m from his eye, clearly. [12]
OR
(B) Draw a ray diagram to show the correction of eye defect of an old man who can not see an object placed closer than 1 m from his eye, clearly. [12]
Answer:
(A) (i) The ciliary muscles contract, making the eye lens thicker and its curvature increases. This decreases the focal length, enabling clear focusing of nearby objects on the retina. (ii) 25 cm to infinity.
OR
(B) (Diagrammatic response required) The diagram should show a hypermetropic eye correction using a convex lens, where virtual rays from an object closer than 1 m are converged to form an image at the near point (>1m), eventually focusing on the retina.
(A) (i) The ciliary muscles contract, making the eye lens thicker and its curvature increases. This decreases the focal length, enabling clear focusing of nearby objects on the retina. (ii) 25 cm to infinity.
OR
(B) (Diagrammatic response required) The diagram should show a hypermetropic eye correction using a convex lens, where virtual rays from an object closer than 1 m are converged to form an image at the near point (>1m), eventually focusing on the retina.
Question 35:
(a) Draw the ray diagram for refraction of light through a glass prism and mark angle of refraction and angle of deviation. [12]
(b) When the path of a light ray refracted through a glass prism is reversed how will the angle of deviation change? [12] Explain. [12]
(b) When the path of a light ray refracted through a glass prism is reversed how will the angle of deviation change? [12] Explain. [12]
Answer:
(a) (Diagrammatic response required) A standard glass prism diagram drawing incident ray, refracted ray, emergent ray. Angle of refraction (\(r\)) is marked inside the prism and angle of deviation (\(\delta\)) is marked between extended incident and emergent rays.
(b) Based on the Principle of Reversibility of Light, if the path of a light ray is reversed, it simply retraces its original path backwards. Consequently, the angle of deviation remains the same.
(a) (Diagrammatic response required) A standard glass prism diagram drawing incident ray, refracted ray, emergent ray. Angle of refraction (\(r\)) is marked inside the prism and angle of deviation (\(\delta\)) is marked between extended incident and emergent rays.
(b) Based on the Principle of Reversibility of Light, if the path of a light ray is reversed, it simply retraces its original path backwards. Consequently, the angle of deviation remains the same.
Question 36:
(a) A ray of light after reflection from a concave mirror becomes parallel to its principal axis. [12] Draw a labelled ray diagram to show this. [12]
(b) (i) Differentiate between the virtual images formed by a convex mirror and concave mirror. [12] (ii) "The value of magnification 'm' for a mirror is -2." [12] Calculate the height of object if the height of image is 20 cm. [12]
(b) (i) Differentiate between the virtual images formed by a convex mirror and concave mirror. [12] (ii) "The value of magnification 'm' for a mirror is -2." [12] Calculate the height of object if the height of image is 20 cm. [12]
Answer:
(a) (Diagrammatic response required) An incident ray passing through the Principal Focus (F) hits the concave mirror and reflects parallel to the principal axis.
(b) (i) A convex mirror always forms a virtual image that is diminished (smaller). A concave mirror forms a virtual image only when the object is very close (between Pole and Focus), and this image is always magnified (larger).
(ii) Magnification \(m = \frac{\text{Height of image } (h')}{\text{Height of object } (h)}\).
Since m = -2, the image is real and inverted, so \(h' = -20\text{ cm}\).
\(-2 = \frac{-20}{h} \implies h = 10\text{ cm}\).
(a) (Diagrammatic response required) An incident ray passing through the Principal Focus (F) hits the concave mirror and reflects parallel to the principal axis.
(b) (i) A convex mirror always forms a virtual image that is diminished (smaller). A concave mirror forms a virtual image only when the object is very close (between Pole and Focus), and this image is always magnified (larger).
(ii) Magnification \(m = \frac{\text{Height of image } (h')}{\text{Height of object } (h)}\).
Since m = -2, the image is real and inverted, so \(h' = -20\text{ cm}\).
\(-2 = \frac{-20}{h} \implies h = 10\text{ cm}\).
Question 37:
(a) Why does an electric bulb become dim when an electric heater in parallel circuit is switched ON? [12]
(b) How to connect three resistors each of resistance 8 \(\Omega\), so that the equivalent resistance of the combination is 12 \(\Omega\)? [12] Draw diagram of the combination and justify your answer. [12]
(b) How to connect three resistors each of resistance 8 \(\Omega\), so that the equivalent resistance of the combination is 12 \(\Omega\)? [12] Draw diagram of the combination and justify your answer. [12]
Answer:
(a) An electric heater draws a very heavy current. This causes a sudden voltage drop in the circuit wires (due to internal resistance of the wiring/source), which reduces the potential difference across the bulb, making it dim.
(b) Connect two 8 \(\Omega\) resistors in parallel, and then connect this combination in series with the third 8 \(\Omega\) resistor.
Justification: Parallel part \(R_p = \frac{8 \times 8}{8 + 8} = 4\ \Omega\).
Total resistance \(R_{eq} = R_p + 8 = 4 + 8 = 12\ \Omega\).
(a) An electric heater draws a very heavy current. This causes a sudden voltage drop in the circuit wires (due to internal resistance of the wiring/source), which reduces the potential difference across the bulb, making it dim.
(b) Connect two 8 \(\Omega\) resistors in parallel, and then connect this combination in series with the third 8 \(\Omega\) resistor.
Justification: Parallel part \(R_p = \frac{8 \times 8}{8 + 8} = 4\ \Omega\).
Total resistance \(R_{eq} = R_p + 8 = 4 + 8 = 12\ \Omega\).
Question 38: Three students Shweta, Ayesha and Samridhi were performing an experiment to understand the factors on which the resistance of a conductor depends. [13] Each one of them completed electric circuit with the help of a cell, an ammeter, a plug key and wire. [13] Shweta put nichrome wire of length 'l' in the circuit and after plugging the key, noted current in the ammeter. [13] Ayesha put nichrome wire of same thickness but twice the length i.e. '2l' in the circuit and after plugging the key, noted current in the ammeter. [13] Samridhi took copper wire of length 'l' and same thickness in the circuit and after plugging the key, noted current in the ammeter. [13]
(a) If the ammeter reading is X ampere with nichrome wire of length 'l', then what will be the ammeter reading if the length of nichrome wire is doubled with same area of cross-section? [13]
(b) What happens to the ammeter reading if the area of cross-section of nichrome wire is doubled, keeping the length of wire 'l' the same? [13]
(c) Define 'resistivity'. [13] Write its SI unit. [13] Compare the resistivity of an alloy with its constituents metals. [13] OR
(c) Give reason: [13] (i) Tungsten is used almost exclusively for making the filament of electric lamps. [13] (ii) Conductors of bread-toasters are made of an alloy rather than a pure metal. [13]
(b) What happens to the ammeter reading if the area of cross-section of nichrome wire is doubled, keeping the length of wire 'l' the same? [13]
(c) Define 'resistivity'. [13] Write its SI unit. [13] Compare the resistivity of an alloy with its constituents metals. [13] OR
(c) Give reason: [13] (i) Tungsten is used almost exclusively for making the filament of electric lamps. [13] (ii) Conductors of bread-toasters are made of an alloy rather than a pure metal. [13]
Answer:
(a) Resistance is directly proportional to length. Doubling length doubles resistance. By Ohm's Law (\(I = \frac{V}{R}\)), current is halved. New reading = \(\frac{X}{2}\) ampere.
(b) Resistance is inversely proportional to cross-sectional area. Doubling area halves resistance. Thus, current doubles. The ammeter reading becomes 2X.
(c) Resistivity is the characteristic resistance offered by a material of unit length and unit cross-sectional area. SI unit: Ohm-meter (\(\Omega\cdot m\)). The resistivity of an alloy is generally higher than that of its constituent pure metals.
OR
(c) (i) Tungsten has a very high melting point and high resistivity; it does not oxidize/burn even at very high temperatures. (ii) Alloys have higher resistivity than pure metals and do not oxidize (burn) readily at high temperatures, making them suitable for heating elements.
(a) Resistance is directly proportional to length. Doubling length doubles resistance. By Ohm's Law (\(I = \frac{V}{R}\)), current is halved. New reading = \(\frac{X}{2}\) ampere.
(b) Resistance is inversely proportional to cross-sectional area. Doubling area halves resistance. Thus, current doubles. The ammeter reading becomes 2X.
(c) Resistivity is the characteristic resistance offered by a material of unit length and unit cross-sectional area. SI unit: Ohm-meter (\(\Omega\cdot m\)). The resistivity of an alloy is generally higher than that of its constituent pure metals.
OR
(c) (i) Tungsten has a very high melting point and high resistivity; it does not oxidize/burn even at very high temperatures. (ii) Alloys have higher resistivity than pure metals and do not oxidize (burn) readily at high temperatures, making them suitable for heating elements.
Question 39:
(A) (i) Draw a diagram showing the magnetic field lines around a bar magnet. [14] Write any two characteristics of magnetic field lines. [14] (ii) Write the statement of Right hand thumb rule. [14] (iii) The concentric circles representing the magnetic field around a current carrying straight wire become larger and larger as we move away from the wire. [14] How does magnetic field change on these concentric circles? [14]
OR
(B) (i) Draw a diagram, showing the magnetic field lines in and around the current carrying solenoid. [14] Write any two salient features of these lines. [14] (ii) What is an electromagnet and how is it made? [14]
OR
(B) (i) Draw a diagram, showing the magnetic field lines in and around the current carrying solenoid. [14] Write any two salient features of these lines. [14] (ii) What is an electromagnet and how is it made? [14]
Answer:
(A) (i) (Diagrammatic response required) Characteristics: 1. They emerge from the North pole and merge at the South pole outside the magnet. 2. Two magnetic field lines never intersect each other.
(ii) Right-Hand Thumb Rule: If you hold a current-carrying straight conductor in your right hand such that the thumb points towards the direction of current, then your fingers will wrap around the conductor in the direction of the magnetic field lines.
(iii) The magnetic field strength decreases as distance from the wire increases (i.e., field strength is inversely proportional to the radius of the circle).
OR
(B) (i) (Diagrammatic response required) Features: 1. Inside the solenoid, the field lines are straight and parallel, indicating a uniform magnetic field. 2. Outside, they curve from one end (North pole) to the other (South pole).
(ii) An electromagnet is a temporary magnet consisting of a coil of insulated wire wound around a soft iron core. It becomes magnetized when electric current passes through the coil and loses magnetism when the current is switched off.
(A) (i) (Diagrammatic response required) Characteristics: 1. They emerge from the North pole and merge at the South pole outside the magnet. 2. Two magnetic field lines never intersect each other.
(ii) Right-Hand Thumb Rule: If you hold a current-carrying straight conductor in your right hand such that the thumb points towards the direction of current, then your fingers will wrap around the conductor in the direction of the magnetic field lines.
(iii) The magnetic field strength decreases as distance from the wire increases (i.e., field strength is inversely proportional to the radius of the circle).
OR
(B) (i) (Diagrammatic response required) Features: 1. Inside the solenoid, the field lines are straight and parallel, indicating a uniform magnetic field. 2. Outside, they curve from one end (North pole) to the other (South pole).
(ii) An electromagnet is a temporary magnet consisting of a coil of insulated wire wound around a soft iron core. It becomes magnetized when electric current passes through the coil and loses magnetism when the current is switched off.
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