1 MARK QUESTIONS
Q1. Which part of the eye can be donated after death?
Q2. Name the part of an eye which is equivalent to
(i) diaphragm and
(ii) photographic plate, in a camera.
Q3. How is the sense of vision carried from the eye to the brain?
Q4. Which liquid fill in the space between eye lens and retina?
Q5. What is the nature of an image formed on the retina of the eye?
Q6. A man is wearing glasses of focal length + 1 m, what can be defect in the eye?
Q7. What is the twinkling of stars due to?
Q8. On what factor does the colour of the scattered light depends?
Q9. Why are danger signal lights red in colour?
Q10. What would have been the colour of the sky, if the Earth had no atmosphere?
Q11. Bees are able to see ultraviolet light. Comment.
Q12. Define power of accommodation.
Q 13. What is the purpose of human eye?
Q14. State one function of iris in human eye.
Q15. What is the nature of image formed on the retina?
Q16. What is meant by dispersion of light?
Q17. What is tyndall effect?
Q18. Name the type of particles which acts as a prism in the formation of rainbow in the sky.
Q19. On which factor does the colour of the scattered white light depend?
Q20. The sky appears dark to passengers flying at a very high altitude. Why?
Q21. What is the cause of dispersion of light passing through a prism?
Q22. Which liquid is filled in the space between eye lens and retina?
Q23. Which part of eye acts as a cable which connects the eye with the brain?
Q24. What is the nature of the image formed on the retina? What kind of lens is present in our eye?
Direction (Q Nos. 25 – 29) In each of the following questions, a statement of Assertion is given by the corresponding statement of Reason. Of the statements, mark the correct answer as
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
(c) If Assertion is true, but Reason is false.
(d) If Assertion is false, but Reason is true.
(e) If Assertion and Reason both are false.
Q25. Assertion: The least distance of distinct vision for a young adult with normal vision is 20 cm.
Reason: Far point for a human eye with normal vision is infinity.
Q26. Assertion: Tyndall Effect is an optical phenomenon of light used to explain atmospheric refraction.
Reason: The tiny particles of dust disperse sunlight in it falls through foliage in a forest.
Q27. Assertion: On a clear summer night twinkling of stars is observed.
Reason: The twinkling of stars is caused by dispersion of star light by the atmosphere.
Q28. Assertion: On mid-day, the colour of the sunlight becomes white.
Reason: No atmospheric refraction is caused due to overhead sun.
Q29. Assertion: Ciliary muscles adjust the size of the crystalline lens inside the human eye.
Reason: Gradual weakening of ciliary muscles leads to astigmatism.
Q30. A person with a myopic eye cannot see object beyond -1.2 m distinctly. The power of the corrective lens used to restore proper vision is
(c) + 0.21 D
(d) +0.91 D
Q31. At noon the sun appears white as:
(a) light is least scattered
(b) all the colours of the white light are scattered away
(c) blue colour is scattered the most
(d) red colour is scattered the most
Q32. The danger signals installed at the top of tall buildings are red in colour. These can be easily seen from a distance because among all other colours, the red light
(a) is scattered the most by smoke or fog
(b) is scattered the least by smoke or fog
(c) is absorbed the most by smoke or fog
(d) moves fastest in air
Q33. A student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his textbook. Which of the following statements is correct?
(a) The near point of his eyes has receded away
(b) The near point of his eyes has come closer to him
(c) The far point of his eyes has come closer to him
(d) The far point of his eyes has receded away
Q34. What is dispersion? What happens when light is passed through a glass prism?
Q35. Why is it difficult to drive on a foggy day?
Q36. Explain, why the Sun overhead at noon, appears white?
Q37. Calculate maximum power of accommodation of a person having normal vision.
Q38. Name the parts of our eyes that help us to focus near and distant objects in quick succession.
3 MARK QUESTION
Q1. Draw a labelled diagram of human eye. What is the significance of the blind spot?
Q2. List two main causes of a person developing nearsightedness. Show with the help of a ray diagram how this defect can be corrected.
Q3. Study the diagram given below and answer the questions that follows:
(i) Which defect of vision is represented in this case? Give reason for your answer.
(ii) What could be the two causes of this defect?
(iii) With the help of a diagram show how this defect can be corrected by the use of a suitable lens?
Q4. Sun is visible 2 min before actual sunrise and 2 min after sunset. Give reason.
Q5. (i) Why does the power to see near objects as well as far off objects clearly diminish
(ii) The far point of a myopic eye is 60 cm. Find the focal length of the lens used to correct it.
Q6. With the help of ciliary muscles, the human eye can change its curvature and thus alter the focal length of its lens. State the changes that occur in the curvature and focal length of the eye lens while viewing:
(a) a distant object,
(b) nearby objects.
Explain, why a normal eye is not able to see distinctly the object placed closer than 25 cm, without putting any strain on the eye.
Q7. Due to gradual weakening of ciliary muscles and diminishing flexibility of the eye lens a certain defect of vision arises. Write the name of this defect. Name the type of lens required by such persons to improve the vision. Explain the structure and function of such a lens.
Q8. (i) Make a ray diagram to show how the eye defect myopia is corrected by using a suitable lens.
(ii) State two reasons due to which this eye defect may be caused.
(iii) A person with myopic eye cannot see objects beyond a distance of 1.5 m. What is the power of the lens required to correct the problem?
Q9. Explain why?
(i) Myopic person prefers to remove his spectacles while reading a book.
(ii) A hypermetropic person prefers to remove the spectacles while looking at the sky?
Q10. A person is unable to see objects nearer than 50 cm. He wants to read a book placed at a distance of 25 cm. Find the nature, focal length and power of the lens he requires for his spectacles.
Q11. What is meant by scattering of light? The sky appears blue and the sun appears reddish at sunrise and sunset. Explain these phenomena with reason.
Q12. How does refraction of light take place in the atmosphere? Explain the reason why stars appear to twinkle and the planets do not twinkle.
Q13. Define angle of deviation. Why do different components of white light split up into spectrum when it passes through a triangular glass prism? Show the angle of deviation for red colour when white light passes through a prism.
Q14. Name the phenomenon associated with the following:
(i) The sky appears blue.
(ii) Formation of a rainbow in the sky.
(iii) Twinkling of stars.
Q15. Explain in brief the reason for each of the following:
(i) The sun appears reddish during sun-rise.
(ii) At noon the sun appears white.
(iii) To an astronaut the sky appears dark instead of blue.
Q16. Describe an activity to show that the colours of white light split by a glass prism can be recombined to get white light by another identical glass prism. Also, draw ray diagram to show the recombination of the spectrum of white light.
Q17. What is Tyndall effect? What is its causes? Name two phenomena observed in daily life which are based on Tyndall effect.
Q18. Draw a labelled diagram of human eye. What is the significance of the blind spot and the yellow spot?
Q19. Describe the formation of rainbow in the sky with the help of suitable diagram.
Q20. List three common refractive defects of vision and suggest the way of correcting these defects.
Q21. State the role of ciliary muscles in accommodation.
Q22. Why we have two eyes to view the objects?
Q23. What is the result of dispersion of white light?
Q24. What is the difference in colours of the Sun observed during sunrise/sunset and noon? Give explanation for each.
Q25. How does the thickness of the eye lens change when we shift looking from a distant tree to reading a book?
Q26. A person got his eyes tested. The optician prescription for the spectacles read.
Left eye= -3 D and right eye= -3.5 D
Discuss the defects of which a person is suffering.
Q27. The power of a lens is +1.5 D. Name the type of defects of vision that can be corrected by using this lens. Find the focal length of the lens.
Q28. A person is able to see objects clearly only when these are lying at distance between 50 cm and 300 cm from his eyes. Name the kind of defects of vision he is suffering from.
Q29. What will be the angle of deviation through a prism angle 60 °, when angles of incidence and emergence are 45° each?
5 MARKS ANSWER
Q1. (i) List three common refractive defects of vision. Suggest the way of correcting these defects.
(ii) About 45 lac people in the developing countries are suffering from corneal blindness. About 30 lac children below the age of 12-year suffering from this defect can be cured by replacing the defective cornea with the cornea of a donated eye. How and why can students of your age involve ‘themselves to create awareness about this fact among people?
Q2. What is atmospheric refraction? Use this phenomenon to explain the following natural events.
(i) Twinkling of stars.
(ii) Advanced sunrise and delayed sunset. Draw diagrams to illustrate your answers.
Q3. What is meant by scattering of light? Mention the factor on which it depends. Explain, why the colour of the clear sky is blue? An astronaut in space finds sky to be dark. Explain reason for this observation.
Q4. (a) Write the function of each of the following parts of human eye: Cornea, iris, crystalline lens, ciliary muscles.
(b) Millions of people of the developing countries of the world are suffering from corneal blindness. These persons can be cured by replacing the defective cornea with the cornea of a donated eye. A charitable society of your city has organized a campaign in your neighbourhood in order to create awareness about this fact. If you are asked to participate in this mission how would you contribute in this noble cause?
(i) State the objective of organizing such campaigns.
(ii) List two arguments which you would give to motivate the people to donate their eyes after death.
(iii) List two values which are developed in the persons who actively participate and contribute in such programmes.
Q5. (a) A student suffering from myopia is not able to see distinctly the objects placed beyond 5 m. List two possible reasons due to which this defect of vision may have arisen. With the help of ray diagrams, explain;
(i) Why the student is unable to see distinctly the objects placed beyond 5 m from his eyes.
(ii) The type of the corrective lens used to restore proper vision and how this defect is corrected by the use of this lens.
(b) If, in this case, the numerical value of the focal length of the corrective lens is 5 m, find the power of the lens as per the new Cartesian sign convention.
Q6. A person is unable to see distinctly the printed on a newspaper. Name the defect of vision he is suffering from. Draw ray diagram to Illustrate this defect. List its two possible causes. Draw a ray diagram to show how this defect may be corrected using a lens of appropriate focal length.
Q7. (i) List three common refractive defects of vision. Suggest the way of correcting these defects.
(ii) About 45 lac people in the developing countries are suffering from corneal blindness. About 30 lac children below the age of 12 years suffering from this defect can be cured by replacing the defective cornea with the cornea of a donated eye. How and why can students of your age involve themselves to create awareness about this fact among people?
Q8. (i) Name the defect of vision in which the eye loses its power of accommodation due to old age.
(ii) The near point of a person suffering from hypermetropia is at 50 cm from his eye. What is the power of the lens needed to correct this defect/ (near point of normal eye is 25 cm)?
(iii) With the help of ray diagrams, show the formation of image by
(a) a hypermetropic eye.
(b) correction of hypermetropia by using an appropriate lens.
Q9. (a) What is presbyopia? State its cause. How is it corrected?
(b) Why does the Sun appear reddish early in the morning? Explain with the help of a labelled diagram.
Q10. (i) Define dispersion of light. How is scattering of light different from dispersion? Give one example of natural phenomenon based on each of these.
(ii) A beam of light consisting of red, blue and yellow colours is incident on the prisms as shown below. Complete the diagram to show refracted and emergent ray.
Q11. (a) Write an activity for observing scattering of light in colloidal solution.
(b) On the basis of this activity explain, why sky appears red at sunrise or sunset.
Q12. (i) Explain, how do we see different colours of an object?
(ii) Why is it so that some people cannot distinguish between different colours?
(iii) A chick wakes up with the sunrise and sleeps by sunset. How does it manage to do so?
Q13. (i) A doctor has prescribed a corrective lens of -4.2 D to a person suffering from defect of vision.
(a) Identify the defect from which he is suffering.
(b) Is the prescribed lens is diverging or converging? Show the nature of the lens with the help of a ray diagram.
(ii) The person wants to read a book placed at 20 cm, whereas near. point of his eye is 30 cm. Calculate the power of lens required.
Q14. (i) List the parts of the human eye that control the amount of light entering into it. Explain, how they perform this function?
(ii) Write the function of the retina in the human eye.
(iii) Do you know that the corneal-impairment can be cured by replacing the defective cornea with the cornea of the donated eye? How and why should we organise groups to motivate the community members to donate their eyes after death?