: CBSE Sample Question Papers

16. The radius of curvature of a convex mirror used on a moving automobile is 2.0 m. A truck is coming behind it at a constant distance of 3.5 m. Calculate (i) the position, and (ii) the size of image relative to the size of the truck. What will be the nature of the image ? 3
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17. (a) Draw a ray diagram to show passage of two rays of light through a rectangular slab of glass, when the angle of incidence is zero in one case and a little less than 90° in the other case. (b) Prove that if a ray enters a rectangular glass slab obliquely and emerges from the opposite face, the emergent ray will be parallel to the incident ray.

OR
(a) State Snell’s law of refraction of light.
(b) A transparent medium A floats on another transparent medium B. When a ray of light travels obliquely from A into B the reflected ray bends away from the normal. Which of the media A and B is optically denser and why ? 3
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18. Name an important ore of aluminium. What are the impurities associated with it? How is pure aluminium obtained from this ore ? Draw a labelled diagram of the plant.

OR
(a) What method for concentration of ore is preferred in each of the following cases and why ?
(i) The ore has higher density particles interspersed with a large bulk of low density impurities. (ii) The ore consists of copper sulphide intermixed with clay particles.
(b) Give an example of amalgams. 5
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19. (a) With the help of a labelled ray diagram show how the image is formed in an astronomical telescope in normal adjustment. Write formulae for
(i) calculating the magnification by the telescope. (ii) finding the length of the tube required for the telescope.
(b) The objective of an astronomical telescope has a focal length of 2.0 m and its eyepiece has a focal length of 0.5 cm. When the telescope is in normal adjustment, find
(i) magnification by the telescope. (ii) the length of the telescope. 5
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20. Name any three forms of energy of the oceans which can be converted into usable energy forms. Describe how it is done in each case. What is the likelihood of their use on a large scale ?

OR
What are (i) solar concentrators and (ii) solar cell panels ? How are they an improvement on simple devices ? Why is it that solar cell panels are costly ? 5
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Section - B

21. State one point of difference between metacentric chromosomes and telocentric chromosomes. 1
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22. Which hormone is responsible for the development of moustache and beard in men ? 1
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23. In terms of evolution, what is the significance of homology between a human hand and awing of a bird ? 2
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24. Draw a labelled diagram of the human urinary system. 2
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25. How can air pollution lead to :
(i) skin cancer in man ? (ii) melting of ice cap of earth ? 2
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26. What is the difference between sensory and motor neutrons ? Which parts of human brain are responsible for auditory reception and sensation of smell ?

OR
What is the importance of the following processes occurring during photosynthesis in plants ? (i) Emission of electrons from chlorophyll. (ii) Photolysis of water. 3
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27. Name any two sexually transmitted diseases (STDs). How do these infectious diseases spread from one person to another ? Give two symptoms of STDs. 3
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28. (i) What does the abbreviation UASB stand for ?
(ii) Explain the process of sewage treatment after it has passed through UASB. 3
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29. Distinguish between aerobic and anaerobic respiration in terms of end-products and energy released. Why do smokers develop an over strained heart ? 3
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30. (i) State two structural differences between an artery and a vein.
(ii) Name a non nucleated cell present in human blood and state one function of this ceil.
(iii) Draw a labelled diagram of human heart. 5
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16. A 5 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm.
The distance of the object from the lens is 30 cm. Find the (i) position, (ii) nature and (iii) size of the
image formed. 3
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17. (i) What is meant by ‘critical angle’ for a ray of light going from one medium into another ?
(ii) What is the consequence of making angle of incidence of light, at an interface, greater than the
critical angle ? (iii) Why does a cut diamond shine more than a glass piece with diamond cut ?

OR
Draw ray diagrams to show the formation of images when the object is placed in front of a concave mirror.
(i) between its pole and focus points.
(ii) between its centre of curvature and focus point. 3
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18. Why is it that iron does not occur as a metal in the crust of the earth ? What are the common compound forms in which iron occurs ? Which of these is more often used for extracting iron ? Why are carbon and limestone mixed with the iron ore before feeding it into the blast furnace ? Write the chemical equations for the reduction step and the slag formation step.

OR
Define an alloy and an amalgam. State the main constituents of the following alloys. In what property is each of them different from its main constituent ?
(i) Stainless steel (ii) Bronze 5
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19. With the help of a labelled ray diagram show the formation of image of an object by a compound microscope.
A compound microscope has an objective of focal length 0,5 cm and an eye-piece of focal length 2.5 cm. /if its tube length is 25 cm, calculate what will be the magnifying power of the microscope. 5
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20. On what principle does a solar water heater operate ? Draw a labelled schematic diagram for a solar / water heater.
The solar constant at a place is 1.4 kW/m², How much solar energy will be received at this place per second over an area of 5 m2 ?

OR
What is the main basic cause for winds to blow ? Name a part of India where wind energy is commercially harnessed. Compare wind power and power of water flow in respect of generating mechanical and electrical energies. What is the hindrance in developing them ? 5
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Section – B

21. State one of the evolutionary forces leading to the origin of a new species according to the synthetic theory of evolution. I
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22. Name the excretory units present in an earthworm. 1
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23. A farmer Hoods his Held every day thinking that watering in this manner will result in a better yield of his wheat crop. What will be the result of this action of the farmer ? 1
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24. Describe how the sex of the offspring is determined in the zygote in human beings. 2
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25. State any two practices which can help in the protection of our environment. 2
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26. Define ‘nerve impulse’. Which structure in a neuron helps to conduct a nerve impulse (i) towards the cell body ?
(ii) away from the cell body ? 3
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27. List the sequence of events that occur during the formation of a blood clot after an injury. 3
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28. What is potable water ? State any four of its necessary characteristics. 3
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29. What is the function of gizzard in a grasshopper ? Draw a labelled diagram showing the digestive system of a grasshopper.

OR
What is the function of epiglottis in man ? Draw a labelled diagram showing the human respiratory
system. 3
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30. With the help of a labelled diagram describe double fertilisation in plants. 5
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16. A convex lens has a focal length of 25 cm. Calculate the distance of the object from the lens if the image is to be formed on the opposite side of the lens at a distance of 75 cm from the lens. What will be the nature of the image ? 3
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17. Name the three primary colours of light. A flower has magenta colour in white light. What will its colour appear to be when viewed separately under each of the lights of primary colours ?
What are complementary colours of light ?
OR
With the help of ray-diagrams show the phenomenon of total internal reflection of light and the concept of critical angle for a transparent medium. 3
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18. (a) Describe briefly the contact process for manufacturing sulphuric acid starting with sulphur. Write the chemical equations for the involved factions.
(b) In this process SO₃ is dissolved in cone. H₂SO₄ and not in water. Why is it so ?
© Name one large industry based on using sulphuric acid.

OR
(a) Draw a flow chart for the manufacture of ammonia gas by Haber’s Process.
(b) How can we show that ammonia is highly soluble in water and gives an alkaline solution.
© Name a major industry using ammonia as basic material. 5
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19. (a) State two main causes of a person developing near sightedness. With the help of a ray-diagram suggest how he can be helped to overcome this disability.
(b) The far point of a myopic person is 150 cm in front of the eye. Calculate the focal length and the power of a lens required to enable him to see distant objects clearly.

OR
(a) How is a simple microscope different from a compound microscope in construction and magnifying power ? A magnifying lens of focal length 6.25 cm is used by a jeweller during his work. His least distance of distinct vision is 25 cm. What magnification is the jeweller getting ?
(b) What is ‘astigmatism1 and how is this vision defect counteracted ? 5 w.
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20. Name the major fuel component of biogas. What are its other combustible components ?
Draw a simple labelled diagram of a fixed dome type biogas plant. What is the use for the residual slurry and why ? 5
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Section-B

21. Write the function of hormone ‘thyroxine’ in our bodies. 1
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22. Name the part of hind brain which takes part in regulation of respiration. 1
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23. Give an example of a vestigeal organ present in human body. 1
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24. Leaves of a healthy ported plant were coated with vaseline to block the stomata. Will this plant remain healthy for long ? State three reasons for your answer. 2
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25. Name two natural agents that can cause erosion of soil. Suggest two ways in which erosion of soil can be checked. 2
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26. (i) Who put forward the double helical model of DNA ‘?
(ii) What are the three chemically essential parts of nucleotides constituting a DNA ?
(iii) How many types of nucleotides are present in a DNA molecule ? 3
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27. What is meant by pollution of air ? Write any two harmful effects of pollution of air. Name any three techniques used for controlling amounts of gaseous pollutants of our atmosphere. 3
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28. (i) When does ovulation occur during the menstrual cycle in a normal healthy woman ?
(ii) Draw a labelled diagram to show the reproductive system of a human female. 3
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29. Explain the process by which inhalation occurs during breathing in human beings.

OR
With the help of a diagram describe the process by which excretion occurs in amoeba. 3
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30. (i) Name the blood vessel that brings oxygenated blood to the human heart.
(ii) Which chamber of human heart receives oxygenated blood ?
(iii) Explain how oxygenated blood from this chamber is sent to all parts of the body. 5
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