CBSE Sample Papers for Class 10 Science Set 11 with Solutions - #NCSOLVE 📚

Students must start practicing the questions from CBSE Sample Papers for Class 10 Science with Solutions Set 11 are designed as per the revised syllabus.

CBSE Sample Papers for Class 10 Science Set 11 with Solutions

Time: 3 Hrs
Max. Marks: 80

General Instructions

• This question paper consists of 39 questions in 3 sections. Section A is Biology, Section B is Chemistry and Section C is Physics.
• All questions are compulsory. However, an internal choice is provided in some questions.
• A student is expected to attempt only one of these questions.

Section – A

Question 1.
Which of the following compounds do not cause thinning of ozone layer? [1]
(a) Chlorofluorocarbon
(b) Carbon tetrachloride
(c) Nitrogen oxide
(d) Methane
Answer:
(d) Methane

Explanation:
Methane is not responsible for depletion of ozone layer. The primary cause of ozone depletion is the presence of chlorine containing source gases (primarily CFCs and related halocarbons), CO₂ and oxides of nitrogen.

Question 2.
Which are the correct statements related to the human nervous system? [1]
(i) Brain is the main coordinating centre of the body.
(ii) Spinal cord mainly controls voluntary actions.
(iii) Cerebrum controls voluntary actions.
(iv) Medulla controls voluntary actions like writing and walking.
(v) Nerves carry messages between different parts of the body and the brain.

(a) (i), (iii), (v)
(b) (ii), (iii), (iv)
(c) (i), (ii), (v)
(d) (iii), (iv), (v)
Answer:
(a) (i), (iii), (v)

Explanation:
The statements (i), (iii) and (v) are correct as brain is the main coordinating system of the body, cerebrum controls voluntary actions, and nerves carry messages between the brain and different parts of the body.

Question 3.
The genotype of the height of an organism is written as Tt. What conclusion can be drawn? [1]
(a) The allele for height has atleast two different genes
(b) There are atleast two different alleles for the gene of height
(c) There are two different genes for height, each having a single allele
(d) There is one allele for height with two different forms
Answer:
(b) There are atleast two different alleles for the gene of height

Explanation:
An allele is a variant form of a gene, which are located at the same position on a chromosome. The heterozygous organism (Tt) shows that it has two different alleles (T-tall and t-dwarf) for the gene of height.

Don’t get confused between genes and alleles. Genes are units of heredity that determine a character, while alleles are the two alternative forms of the same gene.

Question 4.
Select the group of organisms is which food material is broken down outside the body and absorbed? [1]
(a) Mushroom, green plants, Amoeba
(b) Yeast, mushroom, bread mould
(c) Paramecium, Amoeba, Cuscuta
(d) Cuscuta, Lice, Tapeworm
Answer:
(b) Yeast, mushroom, bread mould

Explanation:
Yeast, mushroom and bread mould belong to the same group as all of them are saprophytes and they breakdown and convert complex organic molecules present in dead and decaying matter into simpler substances outside their body.

Question 5.
In 1987, an agreement was formulated by the United Nations Environment Programme (UNEP) to freeze the production of X to prevent depletion of Y. X and Y respectively referred here are [1]
(a) ozone, CFCs
(b) CFCs, UV rays
(c) CFCs, ozone
(d) UV rays, diatomic oxygen
Answer:
(c) CFCs, ozone

Explanation:
In the given question ‘X’ is CFCs, while V is ozone.

Question 6.
Which of the following features relates to biodegradable substances? [1]
(a) Broken down by biological processes
(b) Remain inert
(c) Persist in environment for long time
(d) May harm the ecosystem
Answer:
(a) Broken down by biological processes

Explanation:
Biodegradable substances are easily broken down by biological processes of microbes such as saprophytic fungi and bacteria.

Question 7.
Which of the following is a correct combination of function and organ in the human reproductive system? [1]
(a) Production of sperms: Ovary
(b) Secretion of testosterone: Testis
(c) Development of embryo: Oviduct
(d) Transport of ovum to uterus: Urethra
Answer:
(b) Secretion of testosterone: Testis

Explanation:
Secretion of testosterone: Testis is the correct combination as in males, the testes produce sperms and also secrete the hormone testosterone, which regulates male reproductive functions.

The following two questions consist of two statements – Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below.
(a) Both (A) and (R) are true and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

Question 8.
Assertion (A) Electrical impulses in the human nervous system are transmitted through neurons.
Reason (R) In humans, information is transferred from one neuron to another across synapses using
Answer:
(c) (A) is true but (R) is false.

Explanation:
R can be corrected as
In humans, information is transferred from one neuron to another across synapses using chemical signals.

Question 9.
Assertion (A) AIDS is an incurable and a fatal bacterial infection.
Reason (R) It suppresses the immune system of the body. [1]
Answer:
(d) (A) is false but (R) is true.

Explanation:
A is false, but R is true. A can be corrected as AIDS (Acquired Immuno Deficiency Syndrome) is caused by HTV (Human Immunodeficiency Virus), which is a virus.

Question 10.
Decomposers are important for the stability of an ecosystem. Comment upon the statement with justification. [2]
Answer:
Decomposers, such as bacteria and fungi, break down dead plants and animals into simpler substances, releasing nutrients like nitrogen and phosphorus back into the soil. This recycling of nutrients maintains soil fertility, supports the growth of producers, and keeps the flow of materials in the ecosystem continuous, thereby ensuring its balance and stability of an ecosystem.

Question 11.
Attempt either A or B [2]
A. Leishmania is a protozoan that reproduces by binary fission and causes disease in humans.
(i) Name the disease caused by Leishmania.
(ii) State why binary fission in Leishmania occurs in a definite orientation.
Answer:
(i) Leishmania causes kala-azar in humans.
(ii) Binary fission in Leishmania occurs in a definite orientation because it has a fixed whip-like structure (flagellum) at one end.

Or

B. What is tissue culture? Explain how new plants are produced by this method.
Answer:
Tissue culture is a method of growing new plants from small pieces of plant tissue in a nutrient medium under controlled conditions. The cells divide to form a mass of cells, which later develops shoots and roots. These plantlets are then transferred to soil to grow into new plants.

Question 12.
Aschool science club conducted an experiment on potted plants kept in sunlight. They noted that plants with adequate water supply showed better photosynthesis than plants with less water.
Using this information answer how guard cells play an important role in photosynthesis. [2]
Answer:
In the experiment, plants with enough water had guard cells that became turgid, opening the stomata wide. This allowed more carbon dioxide to enter the leaf, which increased the rate of photosynthesis. In plants with less water, guard cells lost turgidity, causing stomata to close, which reduced carbon dioxide entry and slowed down photosynthesis. Thus, guard cells regulate the opening and closing of stomata, directly influencing the photosynthetic rate.

Question 13.
Draw and explain the structure of the male reproductive system. [3]
Answer:
The male reproductive system consists of a pair of testes, sperm ducts, glands, and a penis. The testes are located in the scrotum and produce sperms and the hormone testosterone. The glands (seminal vesicles and prostate gland secrete fluids that provide nutrition and medium for sperm transport. Sperms travel through the sperm ducts into the urethra, which passes through the penis for transfer into the female reproductive tract.

Question 14.
A student conducted an experiment using a plant to study photosynthesis. The plant was kept under a bright light source for 30 minutes.
(i) Describe how the student can test the presence of starch in the leaf after the experiment.
(ii) What does the result describe about photosynthesis. [3]
Answer:
(i) After the plant was kept under bright light for 30 minutes, a leaf is plucked and boiled in water to stop all chemical activities. Then, it is boiled in alcohol to remove the green pigment (chlorophyll). The leaf is then washed with water and placed on a white sheet. A few drops of iodine solution are added to the leaf. If starch is present, the leaf will turn blue-black.

(ii) The blue-black colour indicates the presence of starch, which means photosynthesis occurred during the exposure to light. This shows that light is necessary for photosynthesis and the plant produced food in the form of starch.

Question 15.
Seema is learning about the human brain and nervous system and how it helps in coordination of different body parts. Answer the questions given below. [4]
Attempt either subpart A or B
A. Name the main parts of the nervous system. Which part of the brain controls voluntary actions like moving your hand?
Answer:
The main parts of the nervous system are the brain, spinal cord, and nerves. The cerebrum is the part of the brain that controls voluntary actions like moving our hand.

Or

B. Some actions like heartbeat and digestion happen automatically without our control. Name the part of the brain that controls these involuntary actions.
Answer:
The part of the brain that controls involuntary actions such as heartbeat and digestion is the medulla oblongata.

C. What is a reflex action and why is it important?
Answer:
A reflex action is an automatic and quick response to a stimulus that does not involve the brain. It is important because it protects the body from sudden harm.

D. The figure given below show the functional unit of the nervous system with parts labelled as L, M, N, O and P. Identify the part where information is acquired by a nerve cell, and explains how an electrical impulse is generated and transmitted in a neuron.

Answer:
The part where information is acquired by a nerve cell is the dendrite. Which is labelled in the figure. An electrical impulse is generated when the dendrite receives a chemical signal, which sets off a chemical reaction that creates and electrical impulse. This electrical impulse travels from the dendrite → cell body → axon → nerve ending. At the axon terminal, the electrical impulse triggers the release of some chemicals, which carry the message across the synapse to the next neuron or target cell.

Question 16.
Attempt either A or B [5]
A. Rajesh is curious about the biological basis of sex-determination in humans. He wants to know how a baby becomes a boy or a girl based on chromosomes.
(i) On what basis is the sex of a newborn baby determined in humans?
(ii) Why is the pair of sex chromosomes called a mismatched pair in males?
Answer:
(i) The sex of a newborn baby in humans is determined by the type of sex chromosome inherited from the father. Females have two X-chromosomes (XX), and males have one X and one Y-chromosome (XY). The mother always gives an X-chromosome, while the father can give either X or Y. If the sperm with X fertilises the egg, the baby is a girl (XX); if the sperm with Y fertilizes the egg, the baby is a boy (XY).

(ii) The pair of sex chromosomes in males is called a mismatched pair because X and Y-chromosomes are different in size and genetic content.
The X-chromosome is larger with many genes, while the Y-chromosome is smaller with fewer genes.

Or
B. Ahaan is learning about some organisms where sex is not decided by chromosomes but by other factors. He wants to understand these different ways of sex-determination.
(i) Name two organisms in which sex is not genetically determined.
(ii) How is the sex determined in these organisms?
Answer:
(i) Two organisms in which sex is not genetically determined are crocodiles and snails.
(ii) In these organisms, sex is determined by environmental or external factors rather than chromosomes. For example, in crocodiles, the temperature at which eggs are incubated decides the sex of the offspring, higher temperatures produce males, while lower temperatures produce females. In snails, sex is determined by environmental conditions and they can change sex during their lifetime. This shows that sex determination in these organisms depends on factors other than genes.

Section – B

Question 17.
Which of the following equations represent redox reactions and what are the values for ‘x, ‘y\ ‘p’ and ‘q’ in these equations? fl]
Equation 1 : MnO₂ + xHCl → MnCl₂ + yH₂O + zCl₂
Equation 2 : Fe₂O₃(s) + 2Al(s) →Al₂O₃(s)+ pFe(Z) + heat
(a) Both equations 1 and 2 are redox reactions; x = 4,y = 2, z = 1 p = 2
(b) Only Equation 1 is redox; x = 2, y = 2, z = 1, p = 3
(c) Only Equation 2 is redox; x = 4, y=2, z = 2, p = 2
(d) Neither equation is redox; x = 6, y= 2, z = 1 p = 1
Answer:
(a) Both equations 1 and 2 are redox reactions; x = 4, y = 2, z = 1 p = 2

Explanation:
Both equations 1 and 2 are redox reactions. The first equation balances with 4 HCl forming 2H₂O and 1 Cl₂, while the second produces 2 Fe atoms.

Question 18.
On the basis of reaction between iron and copper sulphate solution given in the table, identify which sample correctly represents the substance oxidised and the reducing agent respectively? [1]

	Sample	Substance oxidised	Reducing agent
(a)	A	Fe	Fe
(b)	B	Fe	FeSO4
(c)	C	Cu	Fe
(d)	D	CuSO4	Fe

Answer:
(a) The reaction between iron and copper sulphate solution is as follows
CuSO₄ + Fe → Cu + FeSO₄
The substance which gets oxidised is called reducing agent. So, in the given reaction, Fe is oxidised and consequently acts as reducing agent by gaining oxygen atoms to form FeS04.

Question 19.
Which substance is an amorphous form of carbon because it lacks a crystalline structure?
(a) Wood
(b) Oil
(c) Chalk
(d) Coke
Answer:
(d) Coke

Explanation:
Coke is an example of amorphous form of carbon which lacks a crystalline structure.

Question 20.
Raj observed that after the reaction between hydrochloric acid and sodium hydroxide, sodium chloride and water are formed. Then he searched about sodium chloride. Some of his statements about NaCl salt are given listed. . [1]
I. It is also prepared by chlor-alkali process.
II. It is a neutral salt, having pH value = 7 .
III. It is white crystalline solid.
IV. It is a also called rock salt.

Which statements are correct?
(a) I, II and IV
(b) II, III and IV
(c) II, and III
(d) III and IV
Answer:
(b) II, III and IV

Explanation:
Among the given statements related to NaCl, only (I) statement is wrong, because sodium hydroxide (NaOH) is prepared by chlor-alkali process, but not NaCl salt.

Question 21.
The reaction in which one functional group in a chemical compound is replaced by another functional group is known as [1]
(a) addition reaction
(b) combustion reaction
(c) elimination reaction
(d) substitution reaction
Answer:
(d) substitution reaction

Explanation:
Substitution reaction. In this, an atom or a group in a compound is replaced by another atom or a group.

Question 22.
Which law is verified while balancing a chemical equation? [1]
(a) Conservation of energy
(b) Law of constant proportions
(c) Law of conservation of mass
(d) Law of conservation of momentum
Answer:
(c) Law of conservation of mass

Explanation:
Law of conservation of mass is verified while balancing a skeletal chemical equation.

Question 23.
Which of the following is a necessary condition for all chemical reactions? [1]
(a) The reactants should be in the same state.
(b) Energy should be supplied to the reactant.
(c) The reactant should be at the same temperature.
(d) There should be physical contact between the reactants.
Answer:
(c) The reactant should be at the same temperature.

Explanation:
The reactants should be at the same temperature. Otherwise, we would not get the desired products or there are chances that the reaction may not proceed.

The following two cjuestions consist of two statements – Assertion (A) and Reason (R). Answer the question by selecting the appropriate option given below.
(a) Both (A) and (R) are true and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

Question 24.
Assertion (A) Different metals have different reactivities with water and dilute acids.
Reason (R) Reactivity of a metal depends on its position in the reactivity series. [1]
Answer:
(a) Both (A) and (R) are true and (R) is the correct explanation of (A).

Explanation:
The metals present at the top of series are most reactive whereas those which are present at the bottom of series are least reactive.

Question 25.
The molecules of soap are sodium or potassium salts of long-chain carboxylic acids. The following figure shows hydrophobic and hydrophilic ends of a soap molecule. [2]

(a) State the part of soap molecule that attaches itself to dirt when soap is dissolved in water.
(b) How is scum formed?
Answer:
(a) Hydrophobic end also called as tail, i.e., hydrocarbon chain.
(b) When soap reacts with hard water, a white curdy precipitate is formed which is called scum.

Question 26.
Attempt either A or B.
A. An alkali metal A gives a compound B (molecular mass = 40) on reaction with water. The compound B gives a soluble compound C on treatment with aluminium oxide.
(a) Identify A, B and C. (b) Give the chemical reactions involved. [3]
Answer:
Let, the atomic weight of alkali metal A be x.
When A reacts with water, it forms a compound B having molecular mass 40. Let the reaction be
2 A + 2H₂O → 2AOH + H₂↑
(B) = 2AOH
According to the question,
x+ 16+ 1 = 40 (Given)
∴ x = 40 – 17
x = 23

23 is the atomic weight of Na (sodium).
Therefore, the alkali metal (A) is Na and the reaction is

So, compound B is sodium hydroxide (NaOH).
Sodium hydroxide reacts with aluminium oxide (Al₂O₃) to give sodium aluminate (NaAlO₂). Thus, C is sodium aluminate [2]

(b) The reaction involved is

Or

B. P, Q and R are 3 elements which undergo chemical reactions according to the following equations.
(a) P₂O₃ + 2Q → Q₂O₃ + 2P
(b) 3RSO₄ + 2Q → (SO₄)₃ + 3R
(c) 3RO + 2P → P₂O₃ + 3R

Answer the following questions
(i) Which element is most reactive?
(ii) Which element is least reactive?
(iii) State and define the type of reaction listed above.
Answer:
(i) Most reactive metal is Q as it has replaced both P and R from their compounds.
(ii) Elementary R is least reactive as it has been replaced by both P and Q.
(iii) The type of reaction listed above is displacement reaction in which a more reactive element displaces a less reactive element from a compound.

Don’t mistakenly identify the most reactive element as the one getting displaced instead of the one that actually displaces others from their compounds.

Question 27.
The two allotropic forms of carbon is shown below. Allotropic form (A) is a colourless transparent substance while allotropic form (B) is a greyish black and opaque substance. [3]

Answer the following questions using the above given information.
(a) Identify substances A and B.
(b) Write any one difference between the given allotropic forms. ‘
(c) Is allotropic form A or B is a good conductor of electricity? Give reason to justify your answer.
Answer:
(a) Substance A is graphite and B is diamond.
(b) Diamond (B) is quite heavy and extremely hard whereas graphite is lighter than diamond, smooth and slippery to touch.
(c) Allotropic form A, i.e., graphite is a good conductor of electricity due to the presence of free electrons.

Donut make mistake in identifying the allotropes of carbon thinking diamond is greyish, bLack opaque substance and graphite is colourless transparent substance.

Question 28.
While cleaning the kitchen, Aryan found a baking soda packet that had turned lumpy due to moisture. To test it, he added some baking soda to vinegar. He noticed bubbles and a fizzing sound. Then, out of curiosity he passed the gas formed through lime water, which turned milky. He remebered his teacher had said this shows a reaction between an acid and a base. Aryan repeated the activity with different amounts of vinegar and baking soda. His observations are recorded in the table below. [4]

S. No.	Substance Taken	Observation
1	Baking soda + Vinegar	Fizzing with bubbles
2	Gas passed through lime water	Lime water turned milky
3	Vinegar in excess	More fizzing observed
4	Baking soda in excess	Residue of soda left unreacted

Answer the following questions based on the above information.
A. Why did fizzing occur when vinegar was added to baking soda?
(a) Due to the formation of a precipitate.
(b) Because of the release of carbon dioxide gas.
(c) Due to a change in temperature.
Justify your answer.
Answer:
(b) Because of the release of carbon dioxide gas.

Explanation:
The fizzing occurred due to a chemical reaction between the acetic add in vinegar and the sodium bicarbonate (baking soda), which is a base. This reaction produces carbon dioxide gas, water and sodium acetate, resulting in effervescence.

B. Describe the complete chemical change taking place in Aryan’s experiment and write a balanced chemical equation for it.
Answer:
The reaction between baking soda (NaHCO₃) and acetic add (CH₃COOH) is an acid-base reaction that produces sodium acetate (CH₃COONa) water and carbon dioxide. It is an example of a neutralisation reaction with gas evolution.
CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂ ↑

Or

Explain the importance of such acid-base reactions in everyday life.
Answer:
Such reactions are used in baking, fire extinguishers and even as quick lab tests to detect acids and bases.

C. When the gas passed through lime water, it turned milky. Which of the following conclusions is correct and why?
(a) The gas evolved was oxygen.
(b) The solution became acidic.
(c) A combustion reaction occurred.
(d) The gas evolved was carbon dioxide and a precipitation reaction occurred.
Answer:
(d) The gas evolved was carbon dioxide and a precipitation reaction occurred.

Explanation:
When carbon dioxide gas is passed through lime water, it reacts with calrium hydroxide in the lime water to form caldum carbonate, which is insoluble and causes the milky appearance. This confirms the presence of carbon dioxide as the evolved gas.

Question 29.
Attempt either A or B. [5]
A. Some metals react vigorously with air and water, requiring special storage. Answer the following questions based on the properties of such reactive metals, focusing on their reactions with air, water, and acids.
(a) A metal ‘P’ having atomic number 19, is stored under oil because it reacts explosively with air.
Identify the metal ‘P’. ‘
(b) Explain why metal ‘P’ is stored under oil.
(c) Write the balanced chemical equation for the reaction of metal ‘P’ with water.
(d) What happens when metal ‘P’ reacts with dilute hydrochloric acid (HCl)? Write the balanced chemical equation.
(e) Name the gas produced when metal ‘P’ reacts with water. How can this gas be tested in the laboratory?
Answer:
(a) The metal ‘P’ is potassium (K).
(b) Potassium (K) is stored under oil to prevent contad with oxygen and moisture in the air, which would cause it to form oxides and hydroxides.
(c) The balanced chemical equation for the reaction of potassium with water is as follows.
2K(s) + 2H₂O(Z) → 2KOH(aq) + H₂(g) + Heat
(d) Potassium reacts violently with HC1, producing hydrogen gas and potassium chloride. The balanced chemical equation is
2K(s) + 2HCl(aq) → 2KCl(aq) + H₂(g) ↑
(e) Hydrogen gas is produced when potassium reacts with water. Hydrogen gas can be tested in the laboratory by bringing a burning splinter near the gas which bums with a pop sound.

Or

B. The figure given below investigates the conditions under which iron rusts. In tube A, both air and water are present. In tube B, there is no air dissolved in the water. In tube C, the air is dry.

Based on the information given above, answer the following questions.
(a) In which setup (A, B, or C) will the iron nails rust the most? Justify your answer.
(b) Why is anhydrous calcium chloride used in setup C? How does it help in studying rusting?
(c) The oil layer in setup B prevents rusting. Explain the reason behind this observation.
(d) Write the balanced chemical equation for rusting.
(e) If setup A uses boiled distilled water instead, would rusting occur? Give a reason.
Answer:
(a) Iron nails will mst most in setup A (water + air). Rusting requires both oxygen and moisture, which are fully present in setup A. Setups B and C lack one essential condition (air or moisture respectively).

(b) Anhydrous calcium chloride is a drying agent that absorbs moisture. In setup C, it creates a dry air environment, proving rusting requires moisture. This helps isolate role of moisture in corrosion.

(c) The oil layer blocks air (oxygen) from dissolving in water. Since rusting needs oxygen, this prevention shows necessity of oxygen.

(d) The balanced chemical equation for rusting is given below
4Fe + 3O₂ + 2XH₂O → 2Fe₂O • xH₂O(rust)

To get maximum marks, one should correctly write the balanced form of chemical equation.

(e) No, rusting would not occur. Boiled water lacks dissolved oxygen and distilled water has no impurities. Both oxygen and water are needed, but boiling removes O₂.

Section – C

Question 30.
Ravi was solving numerical based on image formation by curved mirrors and he noted the following statements based on his understanding: [1]
I. When an object is placed between the pole and focus of a concave mirror, the image formed is behind the mirror and cannot be captured on a screen.
II. For any real image formed by a concave mirror, the magnification is always positive and less than 1.
III. A convex mirror always forms a virtual image, and the image distance is always less than the focal length.
IV. The mirror formula \(\frac{1}{f}=\frac{1}{v}+\frac{1}{u}\) is applicable for both concave and convex mirrors, but the sign convention must be strictly followed to avoid errors.

Which of the above statements are correct?
(a) I, III and IV
(b) I, II and IV
(c) II, III and IV
(d) I, II and III
Answer:
(a) I, IB, and IV

Explanation:
A concave mirror forms a virtual image behind the mirror when the object is placed between its pole and focus. A convex mirror, on the other hand, always produces a virtual image, and the image distance is always less than its focal length. The mirror formula is applicable to both concave and convex mirrors, provided the sign convention based on the Cartesian coordinate system is correctly followed.

Question 31.
The intensity of scattering is inversely proportional to the fourth power of the wavelength of light, i.e.
I ∝ \(\frac{1}{\lambda^4}\)
Given that the wavelength of blue light is approximately 450 nm and red light is approximately 650 ran, by what factor is blue light scattered more than red light on Earth’s atmosphere?
(a) About 2 times more
(b) About 4 times more
(c) About 6 times more
(d) About 10 times more
Answer:
(b) About 4 times more

Explanation:
\(\frac{I_{\text {blue }}}{I_{\text {red }}}=\left(\frac{\lambda_{\text {red }}}{\lambda_{\text {blue }}}\right)^4=\left(\frac{650}{450}\right)\) = 1.44⁴ ≈ 4

The following two questions consist of two statements – Assertion (A) and Reason (R). Answer the questions by selecting the appropriate option given below. .
(a) Both (A) and (R) are true and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

Question 32.
Assertion (A) When a concave is held under water its focal length will increase.
Reason (R) The focal length of a concave mirror is independent of the medium in which it is placed. [1]
Answer:
(d) (A) is false but (R) is true.

Explanation:
For mirrors, reflection depends on the shape of the surface and not on the refractive index of the surrounding medium; similarly, the focal length depends only on the radius of curvature, not on the surrounding medium. Hence, (A) is false but (R) is true.

Question 33.
The diagram below shows the formation of an image by an optical instrument.

(a) Identify the optical instrument shown as a vertical rectangle in the diagram.
(b) If the object is placed 30 cm from the optical instrument and the image is formed 15 cm on the other side. Calculate the focal length of the instrument using the lens formula.
(c) Mention the type of image is formed (real/virtual, upright/inverted, magnified/reduced)
Answer:
(a) Convex lens
The light converges after passing through the instrument.

(b) Given : u = -30 cm and v = 15 cm
Using, \(\frac{1}{f}=\frac{1}{v}-\frac{1}{u} ; \frac{1}{f}=\frac{1}{15}-\frac{1}{(-30)}=\frac{1}{10}\)
f = 10 cm

To get maximum marks student carefully used proper sign convention in lens formula.

(c) The image formed is real, inverted and diminished.
The image is real (forms on the other side and can be seen on a screen), inverted (arrow points down) and smaller than the object (diminished).

Question 34.
Attempt either A or B.

A. Find out the following in the electric circuit given in the figure.
(i) Determine the total resistance of the entire circuit.
(ii) Difference in the readings of the ammeter A₁ and A₂ if any.
Answer:
(i) Between C and D there are two 8 ohm resistors connected in parallel
Using \(\frac{1}{R_{\text {parallel }}}=\frac{1}{R_1}+\frac{1}{R_2}\)
\(\frac{1}{R_{\text {parallel }}}=\frac{1}{8}+\frac{1}{8}=\frac{1}{4}\)
R_parallel = 4 Ω

Since, all the remaining resisters are connected in series
Using R_series = R₁ + R₂ + R₃
R_series = 10 + 4 + 3 = 17 Ω

(ii) Since, Al is placed before the parallel branch, so the current flowing through it is given by using Ohm’s law
I = \(\frac{V}{R},\),
I = \(\frac{5}{17}\) ≈ 0.29 A
Where, 5V is the battery voltage and 17 Ω is the net equivalent resistance of the circuit.
At point C, the current splits equally into the two 8 Ω resistors (since they are identical), then recombines at point D.
So, A₁ measures the total current: 0.294 A and A₂, placed after the branch, also measures the total current: 0.294 A so there is no difference in A₁ and A₂ reading.

Or

B. An electric lamp of resistance 20 ohm in a conductor of resistance 4 ohm are connected to 6 V battery as shown in the circuit given. Calculate
(i) the total resistance of the circuit
(ii) the current flowing through the circuit and the potential difference across the electric lamp and conductor
Answer:
Given
Resistance of electric lamp = 20 Ω
Resistance of conductor = 4 Ω
Voltage of battery = 6 V

(i) Since, the lamp and conductor are connected in series, the total resistance is given as R = R₁ + R₂
R = 20 + 4 = 24 Ω

(ii) To find the current through the circuit
Using I = \(\frac{V}{R},\)
I = \(\frac {6}{24}\) ≈ 0.25

Uisng V = I × R
V_lamp = I_lamp × R_lamp
V_lamp = 0.25 × 20 = 5 V

Similarly,
V_conductor = I_conductor × R_conductor
V_conductor = 0.25 × 4 = 1 V

Question 35.

The figure shows a defect of vision in which the image is formed at point M when an object is placed at 25 cm.
(i) Identify the defect of vision shown in the figure. State its cause.
(ii) Suggest the type of lens used to correct this defect and explain how it helps?
Answer:
(i) Defect Hypermetropia (farsightedness). Either the eyeball is too short or the eye-lens is too weak, so rays from a nearby object (normal near point, 25 cm) are not focused on the retina but would meet (if extended) behind it – hence image forms behind the retina.

(ii) A convex (converging) lens. The convex lens converges incoming rays before they enter the eye so that the eye’s lens can focus them exactly on the retina.

Question 36.
A science student has a constantan wire of diameter 0.40 mm and needs to make a 1.5 Ω resistor. The resistivity of constantan is 4.9 × 10^-7 Ω. m. [3]
(i) Work out the cross-sectional area of the wire.
(ii) How long should the wire be to get the desired resistance?
Answer:
Given
Resistance (R) = 15 ohm
Diameter (d) = 0.40 mm
Resistivity (p) = 49 × 10^-7 ohm.m

(i) A wire is cylindrical in shape, so the cross-sectional area of the given wire will be the area of the circle
A = πr² = π\(\left(\frac{d}{2}\right)^2\)
A = 3.14 × \(\left(\frac{0.40 \times 10^{-3}}{2}\right)^2\)
= 1.25 × 10^-7 m²

(ii) Using
R = \(\frac{\rho L}{A}\)
1.5 = \(\frac{4.9 \times 10^{-7} \times L}{1.26 \times 10^{-7}}\)
L = \(\frac{1.5 \times 1.26 \times 10^{-7}}{4.9 \times 10^{-7}}\) ≈ 0.3857

Student mass forget to convert diameter into meters and mis apply R = \(\frac{\rho L}{A}\) formula.

Question 37.
A circuit is arranged as shown in the figure. A compass C is placed near the wire XY. Write your opinion in each of the following situation along with your justification. [3]
(i) The magnitude of electric current is increased.
(ii) The compass needle is displaced away from the conductor.

Answer:
(i) When current flows through a wire, it produces a magnetic field around it. The strength of this magnetic field is directly proportional to the magnitude of the current.
So, if the current is increased, the magnetic field around the wire becomes stronger.
This stronger magnetic field exerts a greater force on the magnetic needle of the compass, causing it to deflect more.
(ii) The deflection of the compass needle will decrease. The magnetic field strength decreases with distance from the current-carrying wire. So, moving the compass farther away reduces the effect of the magnetic field, causing less deflection.

Question 38.
When a ray of light moving in a medium enters obliquely in another medium, it bends from its path. This phenomenon is called refraction of light. The ability of a medium to refract light is expressed in terms of optical density. The term optical density is not the same as mass density. If we compare two optical media, the one with the larger absolute refractive index is an optically denser medium than the other. Also, the speed of light through a given medium is inversely proportional to its optical density. [4]
A. Define the term absolute refractive index of a medium.
Answer:
Absolute refractive index of a medium is defined as the ratio of the velocity of light in vacuum to the velocity of light in the medium.

B. Refractive indices of glass, water and carbon disulphide are 1.50,1.33 and 1.62, respectively. In which one of these media is the speed of light (i) highest, and (ii) lowest ?
Answer:
The speed of light is highest in the medium with the lowest refractive index. Therefore, it’s highest in water (1.33) and lowest in carbon disulphide (1.62).

Attempt either C or D
C. The absolute refractive indices of glass and water are 3/2 and 4/3, respectively, If the speed of light in water is 2.25 × 10⁸ m/s, find the speed of light in (i) vacuum, and (ii) glass.
Answer:
For water, n = \(\frac{c_{\text {vacuum }}}{c_{\text {water }}} \Rightarrow \frac{c_{\text {vacuum }}}{2.25 \times 10^8}=\frac{4}{3}\)
Solving for C_vacuum
C_vacuum = n_2water × c_water
= \(\frac {4}{3}\) × 2.25 × 10⁸
= 3 × 10⁸ m/s

Similarly for glass, n_glass = \(\frac{c_{\text {vacuum }}}{c_{\text {glass }}}=\frac{c_{\text {vacuum }}}{c_{\text {glass }}}=\frac{3}{2}\)
Solving for C_glass
C_glass = \(\frac{C_{\text {vacuum }}}{C_{\text {glass }}}\)
⇒ C_glass = \(=\frac{3 \times 10^8}{3 / 2}\)
C_glass = 2 × 10⁸ m/s

Or

D. The absolute refractive indices of glass and water are 3/2 and 4/3, respectively. Find the refractive index of water with respect to glass.
Answer:
The refractive index of water with respect to glass is

So, the refractive index of water with respect to glass is \(\frac {8}{9}\).

Question 39.
The arrangement of resistors shown in the figure below is connected to a battery. A 60 Ω resistor is connected in series with two 30 Ω resistors that are connected in parallel, and the power dissipated in the 60 Ω resistor is 108 W. [5]

Calculate
(i) The current in the circuit
(ii) The potential difference across the 30 Ω resistors (i.e. reading of voltmeter V₂)
(iii) The reading in voltmeter V₁ (connected across the battery)
Answer:
(i) Using P= I²R
108 = I² × 60
I² = \(\frac {108}{60}\) = 1.8
I = 1.34 A

(ii) to find the reading of V₂ we need to know the equivalent resistance
Uisng \(\frac{1}{R}=\frac{1}{R_1}+\frac{1}{R_2}\)
⇒ \(\frac{1}{R}=\frac{1}{30}+\frac{1}{30}=\frac{1}{15}\)

Therefore, from V = I × R
V₂ = 1.34 × 15 = 20.1 V

(iii) V₁ is across the entire battery i.e. complete circuit So, the net resistance in the complete circuit is given by
R = R₁ + R₂
R = 60 + 15 = 75 Ω
Now using ohm’s law, V₁ = 134 × 75 = 100.5 V

Or

Two lamps one rated 100W, 220V and the other 60W, 220V are connected in parallel to electric main supply. Find.
(i) Current drawn by the two bulbs from the line.
(ii) Resistance of each lamp.
(iii) Power dissipation across each lamp.
Answer:
(i) Using P= I × V
For lamp 1 I₁ = \(\frac {100}{200}\) ≈ 0.4545 A
Similarly for lamp 2 I₂ = \(\frac {60}{220}\) ≈ 0.2727 A
Therefore, the net current drawn from the line is I₁ + I₂ = 0.4545 + 0.2727 = 0.727 A

(ii) Using R = \(\frac{V^2}{P}\)
R₁ = \(\frac{220^2}{100}=\frac{48400}{100}\) = 484 Ω
Similarly, R₂ = \(\frac{220^2}{60}=\frac{48400}{60}\) = 806.67 Ω

(iii) Since, each lamp is rated at 220V and they’re
connected to 220V mains, they both operate at their rated voltage. So, the power dissipated is equal to their respective rated power.
Total power dissipated = 100 + 60 = 160 W

The post CBSE Sample Papers for Class 10 Science Set 11 with Solutions appeared first on Learn CBSE.

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