Vardaan Learning Institute

Topic: The Human Eye and the Colourful World

Class: 10 (Science) Type: Bonus Practice Paper Max. Marks: 50
Name:
Date:
SECTION A: OBJECTIVE TYPE QUESTIONS (1 Mark Each)
1. The human eye forms the image of an object at its:
  1. Cornea
  2. Iris
  3. Pupil
  4. Retina
2. The change in focal length of an eye lens is caused by the action of the:
  1. Pupil
  2. Retina
  3. Ciliary muscles
  4. Iris
3. The muscular diaphragm that controls the size of the pupil is the:
  1. Cornea
  2. Ciliary muscles
  3. Iris
  4. Retina
4. The least distance of distinct vision for a young adult with normal vision is about:
  1. 25 m
  2. 2.5 cm
  3. 25 cm
  4. 2.5 m
5. The far point of a healthy, normal eye is at:
  1. 25 cm
  2. Infinity
  3. 100 cm
  4. 50 cm
6. Which of the following phenomena of light are involved in the formation of a rainbow?
  1. Reflection, refraction and dispersion
  2. Refraction, dispersion and total internal reflection
  3. Refraction, dispersion and internal reflection
  4. Dispersion, scattering and total internal reflection
7. A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power:
  1. +0.5 D
  2. -0.5 D
  3. +0.2 D
  4. -0.2 D
8. The defect of vision known as Astigmatism is corrected by using:
  1. Bifocal lens
  2. Cylindrical lens
  3. Concave lens
  4. Convex lens
9. Which of the following colors has the longest wavelength?
  1. Blue
  2. Green
  3. Violet
  4. Red
10. The sky appears blue because:
  1. Blue color is scattered most
  2. Red color is scattered most
  3. Blue light is absorbed least
  4. Red light is absorbed most
Directions (Q11-Q14): In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
11. Assertion (A): The sky appears dark to passengers flying at very high altitudes.
Reason (R): Scattering of light is not prominent at such heights due to lack of atmosphere.
12. Assertion (A): The sun appears white at noon.
Reason (R): At noon, the sun is overhead and light travels a relatively shorter distance, scattering only a little of the blue and violet colours.
13. Assertion (A): Planets do not twinkle.
Reason (R): Planets are much closer to the earth and are seen as extended sources of light.
14. Assertion (A): Danger signals are made of red colour.
Reason (R): The red colour is scattered the least by fog or smoke.
SECTION B: SHORT ANSWER QUESTIONS (3 Marks Each)
15. What is meant by power of accommodation of the eye? Corrective lenses for which two defects use the power of accommodation concept? (Actually, no, lenses replace accommodation limitations. Just define it.) Define power of accommodation and state its value for a normal eye.
16. A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision? Calculate its power.
17. Why do we have two eyes instead of one? State two advantages.
18. Why do stars twinkle? Explain.
19. Draw a ray diagram to show the refraction of light through a triangular glass prism. Label the angle of deviation.
20. What is Presbyopia? State its cause and correction.
SECTION C: LONG ANSWER QUESTIONS (5 Marks Each)
21. (i) What is Hypermetropia? State two causes of this defect.
(ii) With the help of a ray diagram, show how this defect is corrected.
(iii) A person needs a lens of power +1.5 D for correction of her vision. What kind of defect is she suffering from? Find the focal length of the corrective lens.
22. (i) Demonstrate the method to recombine the spectrum of white light.
(ii) Why is the colour of the clear sky blue?
(iii) Why does the sun appear reddish early in the morning?
SECTION D: CASE STUDY (4 Marks)
23. Read the following text and answer the questions:
Isaac Newton was the first to use a glass prism to obtain the spectrum of sunlight. He tried to split the colours of the spectrum of white light further by using another similar prism but he could not get any more colours. He then placed a second identical prism in an inverted position with respect to the first prism. This allowed him to recombine the spectrum into white light.

(i) Which colour of light bends the least when white light passes through a prism? (1 Mark)
(ii) Which colour bends the most? (1 Mark)
(iii) What is the order of colours in the spectrum of white light? (2 Marks)
24. Read the following text and answer the questions:
Atmospheric refraction is the phenomenon of bending of light on passing through the earth's atmosphere. This causes several optical phenomena like twinkling of stars, advanced sunrise, and delayed sunset. The density of the atmosphere changes with altitude, causing light to bend.

(i) By how much time is the sunrise advanced and sunset delayed due to atmospheric refraction? (1 Mark)
(ii) Why do stars appear slightly higher than their actual position? (1 Mark)
(iii) Why do planets not twinkle? (2 Marks)
"All the best!"