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CBSE Sample Papers for Class 10 SA2 Science Solved 2016 Set 2

SECTION A

1. Write the name and formula of the 2nd member of homologous series having general formula  cnH2n.
2. Name two simple organisms having the ability of regeneration.
3. What will be the amount of energy available to the organisms of the 2nd trophic level of a food chain, if the energy available at the first trophic level is 10, 000 joules ?
4. Draw a labelled diagram to illustrate energy flow in an ecosystem. (HOTS)
5. “The chromosomal number of the sexually producing parents and their offspring is the same.”  Justify this statement.       (HOTS)
6. State the structure of iris and its function in human eye. ‘
7. Draw the structures of the following compounds and identify the functional group present in them:
(i) Butanoic acid
(ii) Bromopropane
(iii) Butyne
8. (a) Write the chemical names of CH3COCH3, C2H5
(b) What happens when acetic acid and ethanol reacts in presence of concentrated H2S04 ? Write the reactions there in.
9.  State the modern periodic law for classification of elements. How many (a) groups and (b) periods are there in the modern periodic table ?
10. Four elements P, Q, R and S have atomic numbers 12,13,14 and 15, respectively.
Answer the following questions giving reasons :
(a) What is the valency of Q ?
(b) Classify these elements as metals and non-metals.
(c) Which of these elements will form the most basic oxide ?
11. The process of spore formation takes place in many simple multicellular organisms which have certain reproductive parts that can be identify.
(a) Name the organism using this process.
(b) Name the reproductive and non-reproductive parts of such organisms.
12. What are three advantages of vegetative propagation ?
13. Evolution is the change in the inherited traits of a population of organisms through successive generations. After a population splits into smaller groups, these groups evolve independently and diversify into new species. A hierarchy of anatomical and genetic similarities, geographical distribution of similar species and the fossil record indicate that all organisms are descended from a common ancestor. Laetoli is a site of Tanzania famous for its hominid (human and its fossil ancestors) footprints, preserved in volcanic ash.
Questions:
(i) What is the main reason for evolution according to Darwin ?
(ii) ‘Both Human beings andchimpanzee have a common ancestor’. Justify the statement by giving reason behind the conclusion.
14. (i) Define Genetics.
(i) Who is regarded as the ‘Father of Genetics’ ? Name the plant on which he performed his experiment.
(ii) Why did he selected that specific plant for his experiments ? (Value Based Question)
15. Some persons have difficulty to see the objects in dim light during night. This is due to the lack of vitamin A in the diet and improper functioning of rod-shaped cells. The rod-shaped cells respond to intensify variation in light. These days, it is possible to correct the defect of vision by using contact lenses.
(i) Identify the defect of eye.
(ii)’The people with this defect of eye are treated with care and proper diet.’ Suggest two reasons.
16. (i) What is meant by ‘least distance of distinct vision’ ?
(ii) How does iris controls the size of the pupil in bright light and dim light ?
17. A narrow beam PQ of white light is passing through a glass prism ABC as shown in the diagram.
cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-17
Trace it on your answer sheet and show the path of the emergent beam as observed on the screen DE.
(i) Write the name and cause of the phenomenon observed.
(ii) Where else in nature is this phenomenon observed ?
(iii) Based on this observation, state the conclusion which can be drawn about the constituents of white light.
18. Draw a ray diagram to show the path of the reflected ray in each of the following cases. A ray of light incident on a convex mirror
(a) Strikes at its pole making an angle 0 from the principal axis.
(b) Is directed towards its principal focus.
(c) Is parallel to its principal axis.
19. Elements forming ionic compounds attain noble gas electronic configuration by either gaining or  losing electrons from their valence shells. Explain giving reason why carbon cannot attain such a configuration in this manner to form its compounds. Name the type of bonds formed in ionic compounds and in the compounds formed by carbon. Also explain with reason why carbon compounds are generally poor conductors of electricity.         (HOTS)
20. (a) Explain whether traits like eye colour or height is genetically inherited. Do power to lift weights  and reading french also belong to the same category ?
(b) How do variations affect the evolution of those organisms that reproduce sexually ?
21. (a) Give one example each of a unisexual and a bisexual flower.
(i) Mention the changes a flower undergoes after fertilisation.
(ii) How does the amount of DNA remain constant though each new generation is a combination of DNA copies of two individuals ?
22. (i) 4-5 cm needle is placed 12 cm away from a convex mirror of focal length 15 cm. Give the location  of the image and the magnification. Describe what happens as the needle is moved farther from the mirror.
(ii) What kind of mirror is used in a solar furnace ? Give reason for using this mirror.
(iii) One half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object ? Justify your answer.
23. Name the eye defect in which eye lens becomes cloudy or milky. Mention the method for its correction. A person uses a lens of power -1.0 D for correcting his distant vision and for correcting his near vision he uses a lens of power + 2.0 D. Calculate the focal length of the lenses required to correct these defects. Explain why a normal eye is not able to see clearly the objects placed closer than the near points.
24. Define the following terms :
(i) Coliform,
(ii) Recycling,
(iii) Sustainable development,
(iv)Chipko Andolan,
(v) Watershed management.

SECTION-B

25. Among the two test-tubes I and II, one contains acetic acid and another contains water. Which of the properties of acetic acid can be used to identify acetic acid from it?
cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-25
I. Colour change with universal indicator
II. Reaction with NaHC03
III. Colour of the solution
IV. Transparent nature
(A) I and II
(B) II and III
(C) III and IV
(D) I and IV
26. Select the correct observation about dilute solution of acetic acid.
(A) It smells like rotten egg and turns blue litmus red
(B) It smells like vinegar and turns red litmus blue.
(C) It smells like rotten egg and turns red litmus blue.
(D) It smells like vinegar and turns blue litmus red.
27. A student takes sodium hydrogen carbonate powder in a test-tube and pours 4-5 drops of acetic acid over it. He observes :
(A) No reaction in the test-tube
(B) Bubbles of a colourless and odourless gas
(C)  A colourless gas with a pungent smell
(D) Evolution of brown coloured gas along with a brisk effervescence in the test-tube.
28. At the end of binary fission :
(A) Two daughter nuclei are formed
(B) A parent cell and a daughter cell are  produced
(C) Identification of parent cell is lost
(D) Both (A) and (B) take place.
29. Select the incorrect statement about budding :
(A) A bud always arises from a particular region on the parent body.
(B) A bud may arise from any part of the parent cell.
(C) Before detaching from the parent body a bud may form another bud.
(D) A bud may separate from the parent body and develop into a new individual.
30. Reena was given two permanent slides, one of binary fission in Amoebaand the other of budding in yeast. She was asked to identify a difference in the nucleus of the two processes. She identified correctly the presence of :
(A) One nucleus in Amoebaand two in yeast, one in bud
(B) Two nuclei in centrally constricted Amoeba,one in yeast cell, one in bu
(C) Two distinct nuclei in Amoeba,one in yeast cell and two in bud
(D) Single nucleus each in Amoebaand yeast cell, and one in its attached bud.
31. A student has obtained an image of a well-illuminated distant object on a screen to determine the focal length,  F1  of the given spherical mirror. The teacher then gave him another mirror of focal length, F2 and asked him to obtain a focussed image of the same object on the same screen. The student found that in order to focus the same object using the second mirror, he has to move the mirror away from the screen. From this observation it may be concluded that both the spherical mirrors given to the student were (select the correct option):
(A) Concave and F1< F2                                                                 (B) Concave and F1 > F2
(C) Convex and F1 < F2                                                                   (D) Convex and  F1 > F2
32. A student focussed the Sun rays using an optical device ‘X’ on a screen S as shown.
cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-32
From this it may be concluded that device ‘X’ is a (select the correct option)
(A) Convex lens of focal length 10 cm.       (B) Convex lens of radius of curvature 20 cm.
(C) Convex lens of focal length 20 cm. (D) Concave mirror of focal length 20 cm.
33. After tracing the path of a ray of light passing through a rectangular glass slab for four different values of  the angle of incidence, a student reported his observations in tabular form as given below:
cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-33
The best observation is :
(A) I
(B) II
(C) III
(D) IV
34. Na, Mg, A1 and P belong to 3rd period but are placed in first, second, thirteenth and fifteenth group. Number of shells occupied in Mg is three. What is the number of occupied shells in Na, A1 and P Give reasons for your answer.
35. Draw a labelled longitudinal structure of a flower showing its parts.
36. Light enters from air into glass plate which has refractive index 1-5. Calculate the speed of light in glass (velocity of light in air is 3 x 108 m/s).

Answers

SECTION A

1. Write the name and formula of the 2nd member of homologous series having general formula  cnH2n.
Ans. Name — Propene
Formula — C3H6                                                                                                                             [CBSE Marking Scheme, 2015]

2. Name two simple organisms having the ability of regeneration.
Ans.  Planaria and Hydra  [CBSE Marking Scheme, 2015]

3. What will be the amount of energy available to the organisms of the 2nd trophic level of a food chain, if the energy available at the first trophic level is 10, 000 joules ?
Ans.  Only 10 percent energy is available from the first trophic level to second trophic level.
= 1000 joules   [CBSE Marking Scheme, 2015]

4. Draw a labelled diagram to illustrate energy flow in an ecosystem. (HOTS)
Ans.  Energy flow is unidirectional, dissipated at each level
cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-a4
[CBSE Marking Scheme, 2015] 1 + 1

5. “The chromosomal number of the sexually producing parents and their offspring is the same.”  Justify this statement.       (HOTS)
Ans.  The first step in sexual reproduction is gamete formation. In this step, the number of  chromosomes gets halved. Thus, each gamete receives half the number of chromosomes to that of somatic cells. During fertilisation, the fusion of male and female gametes takes place, which results in the number of chromosomes in the zygote to be equal to that of somatic cells. Thus, the chromosomal number of the sexually producing parents and their offspring is the same

6. State the structure of iris and its function in human eye. ‘
Ans.  Just behind the cornea is a dark coloured muscular diaphragm which has a small circular opening in the middle. Iris is made of muscles. They control the size of opening of pupil. 2  [CBSE Marking Scheme, 2014]

7. Draw the structures of the following compounds and identify the functional group present in them:
(i) Butanoic acid
(ii) Bromopropane
(iii) Butyne
Ans.cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-a7

8. (a) Write the chemical names of CH3COCH3, C2H5
(b) What happens when acetic acid and ethanol reacts in presence of concentrated H2S04 ? Write the reactions there in.
Ans. cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-a8

9.  State the modern periodic law for classification of elements. How many (a) groups and (b) periods are there in the modern periodic table ?
Ans.  
 “Properties of elements are the periodic function of their atomic number.”
(a) There are 18           3
(b) There are 7 periods in the modern periodic table. [C.B.S.E. Marking Scheme, 2012]

10. Four elements P, Q, R and S have atomic numbers 12,13,14 and 15, respectively.
Answer the following questions giving reasons :
(a) What is the valency of Q ?
(b) Classify these elements as metals and non-metals.
(c) Which of these elements will form the most basic oxide ?
Ans.  
(a) The valency of Q is 3 as its valence shell has three electrons in it.
(b) Elements P and Q are metals as they have 2 electron in their valence shell and they are positively charged ions whereas elements R and S are non-metals as they gain electrons to complete their octet.
(c) P and Q will form basic oxides as they are metals. 1 + 1 + 1

11. The process of spore formation takes place in many simple multicellular organisms which have certain reproductive parts that can be identify.
(a) Name the organism using this process.
(b) Name the reproductive and non-reproductive parts of such organisms.
Ans.  
(a) Rhizopus.
(b) Reproductive-Sporangia.
Non-reproductive-Hyphae      [CBSE Marking Scheme, 2015] 3

12. What are three advantages of vegetative propagation ?
Ans.  
Three advantages of vegetative propagation:
(i) Plants which do not produce viable seeds can be produced by this method.
(ii) Plants raised by this method can bear flowers and fruits earlier than those produced from seeds.
(iii) The characters (traits) of the parent plant can be preserved by this method.
(iv) It is cheap, easier and more rapid method of propagation.
(v) Superior quality of plants can be obtained. [CBSE Marking Scheme, 2015] 3

13. Evolution is the change in the inherited traits of a population of organisms through successive generations. After a population splits into smaller groups, these groups evolve independently and diversify into new species. A hierarchy of anatomical and genetic similarities, geographical distribution of similar species and the fossil record indicate that all organisms are descended from a common ancestor. Laetoli is a site of Tanzania famous for its hominid (human and its fossil ancestors) footprints, preserved in volcanic ash.
Questions:
(i) What is the main reason for evolution according to Darwin ?
(ii) ‘Both Human beings andchimpanzee have a common ancestor’. Justify the statement by giving reason behind the conclusion.
Ans.  
(i) Natural Selection leads to an evolutionary change when some individuals with certain traits  in a population have a higher survival and reproductive rate than others and pass on these inheritable genetic features to their offspring.
(ii) It is for sure that we have similar characteristics as chimpanzees because both humans and chimpanzees evolved from a common ancestor.
Scientists have explained origin of humans in an evolutionary perspective. Evolution of human beings is being updated with several changes in anthropology, palaentology and molecular biology. Chimpanzees, Gorillas, Orungutans and human beings belong to homimdae family. These are some evidences of homology of human beings with that of chimpanzee at chromosomal level.
(a) Humans and chimpanzees have a common point the larynx between the pharynx and the lungs as present in their common ancestor.
(b) Orrorin is the early species of Homininae estimated at 6.1 to 5.7 million year. This human  resembled chimpanzee in hominin line.    3
[CBSE Marking Scheme, 2014, 8XSVHLC ]

14. (i) Define Genetics.
(i) Who is regarded as the ‘Father of Genetics’ ? Name the plant on which he performed his experiment.
(ii) Why did he selected that specific plant for his experiments ? (Value Based Question)
Ans.  
(i) Genetics is the branch of biology tha deals with that study of heredity and variations.
(ii) Gregor Johann Mendel, garden pea.
(iii) Garden pea plants were easily available / they grow in one season / fertilization was easy.[CBSE Marking Scheme, 2012] 3

15. Some persons have difficulty to see the objects in dim light during night. This is due to the lack of vitamin A in the diet and improper functioning of rod-shaped cells. The rod-shaped cells respond to intensify variation in light. These days, it is possible to correct the defect of vision by using contact lenses.
(i) Identify the defect of eye.
(ii)’The people with this defect of eye are treated with care and proper diet.’ Suggest two reasons.
Ans.  
(i) Night blindness.
(ii) (a) Proper diet provide Vitamin A to reduce this defect.
(b) Taking care of eyes for proper functioning of rod-shaped cells. 3

16. (i) What is meant by ‘least distance of distinct vision’ ?
(ii) How does iris controls the size of the pupil in bright light and dim light ?
Ans.  
(i) The minimum distance at which objects can be seen most distinctly without strain is called the  least distance of distinct vision.
(ii) In bright light, the iris contracts the pupil to allow less light to enter the eye. In dim light, the iris expands the pupil to allow more light to enter the eye.

17. A narrow beam PQ of white light is passing through a glass prism ABC as shown in the diagram.
cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-17

Trace it on your answer sheet and show the path of the emergent beam as observed on the screen DE.
(i) Write the name and cause of the phenomenon observed.
(ii) Where else in nature is this phenomenon observed ?
(iii) Based on this observation, state the conclusion which can be drawn about the constituents of white light.
Ans. cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-a17
(i) The phenomenon of splitting up of white light into its constituent colours is called dispersion of light.  Dispersion of light is caused because different constituent colours of light offer different refractive indexes to the material of the prism.
(ii) The formation of rainbow is caused by the dispersion of the white sunlight into its constituent colours.
(iii) Based on the dispersion of white light into its constituent colours, we can conclude that:
(a) the white light consists of seven colours.
(b) the violet light suffers maximum deviation and the red light suffers minimum deviation. 1 + 1/2 +1/2 + 1

18. Draw a ray diagram to show the path of the reflected ray in each of the following cases. A ray of light incident on a convex mirror
(a) Strikes at its pole making an angle 0 from the principal axis.
(b) Is directed towards its principal focus.
(c) Is parallel to its principal axis.
Ans. cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-a18.1
cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-a18.2

19. Elements forming ionic compounds attain noble gas electronic configuration by either gaining or  losing electrons from their valence shells. Explain giving reason why carbon cannot attain such a configuration in this manner to form its compounds. Name the type of bonds formed in ionic compounds and in the compounds formed by carbon. Also explain with reason why carbon compounds are generally poor conductors of electricity.         (HOTS)
Ans.  Carbon has 4 electrons in its outermost shell. It cannot lose 4 electrons to form C4+ because very high energy is required to remove 4 electrons. ‘          1.1/2
In cannot gain 4 electrons to form C4- ions because it is difficult for 6 protons to hold on to 10 electrons.  1.1/2
> Ionic/Electrovalent Bonds.  1/2
> Covalent bonds.              1/2
> There are no charged particles in carbon compounds and hence poor conductors of electricity. 1  [CBSE Marking Scheme, 2015]

20. (a) Explain whether traits like eye colour or height is genetically inherited. Do power to lift weights  and reading french also belong to the same category ?
(b) How do variations affect the evolution of those organisms that reproduce sexually ?  
Ans.(a) Yes, eye colour and height are genetically inherited traits, as these are expressed by genes. No, weight lifting and reading French are acquired traits. 3
(b) Variations in individuals^during sexual reproduction gives survival advantages to them, and help them to adapt even in extreme environments.   [CBSE Marking Scheme, 2015] 2

21. (a) Give one example each of a unisexual and a bisexual flower.
(i) Mention the changes a flower undergoes after fertilisation.
(ii) How does the amount of DNA remain constant though each new generation is a combination of DNA copies of two individuals ?
Ans.  (a) Unisexual flowers : Cucumber, pumpkin, water melon, papaya, etc.
Bisexual flowers: Hibiscus, rose, lily, etc. (Any one example)
(b) Changes in a flower after fertilisation : The outer layers of the ovule become impervious and hard and function as a seed coat. An ovule with an embryo inside is called a seed.
The ovary enlarges and ripens to become a fruit. Other floral parts such as sepals, petals, stamens, styles and stigma may fall off. However, in some cases, they remain persistent in the fruit.
(b) Deoxyribonucleic acid (DNA) copying is an essential part of reproduction, as it passes genetic  information from parents to offspring. The reproducing cells produce a copy of their DNA through some chemical reactions and result in two copies of DNA. The copying of DNA always takes place along with the creation of additional cellular structure. This process is then followed by the division of a cell into two cells. In this way, the amount of DNA remains constant through each new generation. 1 + 2+2

22. (i) 4-5 cm needle is placed 12 cm away from a convex mirror of focal length 15 cm. Give the location  of the image and the magnification. Describe what happens as the needle is moved farther from the mirror.
(ii) What kind of mirror is used in a solar furnace ? Give reason for using this mirror.
(iii) One half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object ? Justify your answer.
Ans. cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-a22
As the needle is moved farther from tire mirror, image moves to the focus and the size of image goes on decreasing
(ii) Concave mirrors are used in solar furnaces as they concentrate solar energy in the focal plane  and help in attaining high temperatures. 1
(iii) When one half of a convex lens is covered with a black paper, the lens will produce a complete  image of the object but the intensity of the image is reduced because rays from the top portion of the lens are only refracted and forms the image.                       [CBSE Marking Scheme, 2011]

23. Name the eye defect in which eye lens becomes cloudy or milky. Mention the method for its correction. A person uses a lens of power -1.0 D for correcting his distant vision and for correcting his near vision he uses a lens of power + 2.0 D. Calculate the focal length of the lenses required to correct these defects. Explain why a normal eye is not able to see clearly the objects placed closer than the near points.
Ans. (a)  Something, the crystalline lens of people at old age becomes milky and cloudy. This condition is called cataract. This causes partial or complete loss of vision.
It is possible to restore vision through a cataract surgery.
(b) Focal length for lens for distance vision  = 1/1=1
Focal length for lens for near vision       = +1/2=+0.5
(c) The focal length of eve lens cannot be decreased below a certain minimum limit. If we try to read a printed page by holding it very close to our eyes, We may see the image being blurred or feel strain in the eve. lo see an object comfortably and distinctly, we must hold it at about 25 cm from the eves.     [CBSE Marking Scheme, 2015] 5

24. Define the following terms :
(i) Coliform,
(ii) Recycling,
(iii) Sustainable development,
(iv)Chipko Andolan,
(v) Watershed management.
Ans. (i)  Coliform : A group of bacteria found in human intestines, whose presence in water indicates contamination by disease-causing microorganisms.
(ii) Recycling: The act of processing used or abandoned materials for creating new products.
(iii) Sustainable development: A pattern of resources used for obtaining economic and social growth of the present generation while preserving the resources for the needs of future generations.
(iv) Chipko Andolan: A grass root level movement in which the villagers used to hug the forest trees and prevent their mass felling by the contractors.
(v) Watershed management: A scientific method of developing land and water resources to increase  the biomass production without causing ecological imbalance. 1×5 = 5

SECTION-B

25. Among the two test-tubes I and II, one contains acetic acid and another contains water. Which of the properties of acetic acid can be used to identify acetic acid from it ?
cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-25
I. Colour change with universal indicator
II. Reaction with NaHC03
III. Colour of the solution
IV. Transparent nature
(A) I and II
(B) II and III
(C) III and IV
(D) I and IV
Ans. (A)  I and II

26. Select the correct observation about dilute solution of acetic acid.
(A) It smells like rotten egg and turns blue litmus red
(B) It smells like vinegar and turns red litmus blue.
(C) It smells like rotten egg and turns red litmus blue.
(D) It smells like vinegar and turns blue litmus red.
Ans.  (D) It smells like vinegar and turns blue litmus red.

27. A student takes sodium hydrogen carbonate powder in a test-tube and pours 4-5 drops of acetic acid over it. He observes :
(A) No reaction in the test-tube
(B) Bubbles of a colourless and odourless gas
(C)  A colourless gas with a pungent smell
(D) Evolution of brown coloured gas along with a brisk effervescence in the test-tube.
Ans. (B)  Bubbles of a colourless and odourless gas.

28. At the end of binary fission :
(A) Two daughter nuclei are formed
(B) A parent cell and a daughter cell are  produced
(C) Identification of parent cell is lost
(D) Both (A) and (B) take place.
Ans.  (A) Two daughter nuclei are formed.

29. Select the incorrect statement about budding :
(A) A bud always arises from a particular region on the parent body.
(B) A bud may arise from any part of the parent cell.
(C) Before detaching from the parent body a bud may form another bud.
(D) A bud may separate from the parent body and develop into a new individual.
Ans. (A)  A bud always arises from a particular region on the parent body.

30. Reena was given two permanent slides, one of binary fission in Amoebaand the other of budding in yeast. She was asked to identify a difference in the nucleus of the two processes. She identified correctly the presence of :
(A) One nucleus in Amoebaand two in yeast, one in bud
(B) Two nuclei in centrally constricted Amoeba,one in yeast cell, one in bud.
(C) Two distinct nuclei in Amoeba,one in yeast cell and two in bud
(D) Single nucleus each in Amoebaand yeast cell, and one in its attached bud.
Ans. (B)  Two nuclei in centrally constricted Amoeba, one in yeast cell, one in bud.

31. A student has obtained an image of a well-illuminated distant object on a screen to determine the focal length,  F1  of the given spherical mirror. The teacher then gave him another mirror of focal length, F2 and asked him to obtain a focussed image of the same object on the same screen. The student found that in order to focus the same object using the second mirror, he has to move the mirror away from the screen. From this observation it may be concluded that both the spherical mirrors given to the student were (select the correct option):
(A) Concave and F1< F2                                                                 (B) Concave and F1 > F2
(C) Convex and F1 < F2                                                                   (D) Convex and  F1 > F2
Ans.  (A) Real and inverted image is formed by the concave mirror. As mentioned, in the second case, the  image distance (v) is increasing. Well-illuminated distant object i.e. object is at infinity. Therefore, F1<F2.

32. A student focussed the Sun rays using an optical device ‘X’ on a screen S as shown.
cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-32
From this it may be concluded that device ‘X’ is a (select the correct option)
(A) Convex lens of focal length 10 cm.      
(B) Convex lens of radius of curvature 20 cm.
(C) Convex lens of focal length 20 cm.
(D) Concave mirror of focal length 20 cm.
Ans. (C)  Convex lens of focal length 20 cm.

33. After tracing the path of a ray of light passing through a rectangular glass slab for four different values of  the angle of incidence, a student reported his observations in tabular form as given below:
cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-33
The best observation is :
(A) I
(B) II
(C) III
(D) IV
Ans.  Observation III will give the best result because it has the largest angle of incidence, due to  which the lateral displacement between the incident ray and the emergent ray will be maximum for  light rays passing through a glass slab.

34. Na, Mg, A1 and P belong to 3rd period but are placed in first, second, thirteenth and fifteenth group. Number of shells occupied in Mg is three. What is the number of occupied shells in Na, A1 and P Give reasons for your answer.
Ans.  It is three in Na, A1 and  P.
Elements with the same number of occupied shells are placed in same period.
[CBSE Marking Scheme, 2012] 1 + 1

35. Draw a labelled longitudinal structure of a flower showing its parts.
Ans. cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-a35

36. Light enters from air into glass plate which has refractive index 1-5. Calculate the speed of light in glass (velocity of light in air is 3 x 108 m/s).
Ans.  cbse-sample-papers-for-class-10-sa2-science-solved-2016-set-2-a36

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