Question 1 :- The human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to
Answer: (b) Accommodation
Question 2 - The human eye forms the image of an object at its
Answer:- (d) Retina
Question 3 :- The least distance of distinct vision for a young adult with normal vision is about
Answer: (c) 25 cm
Question 4 :- The change in focal length of an eye lens is caused by the action of the
Answer: (c) Ciliary muscles
Question 5 - A person needs a lens of power 5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision?
Answer: The power of a lens can be calculated by following formula:
Hence, the focal length of the required lens for near vision = +0.67 cm
Question 6 - The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
Answer: In the given situation, the person shall be able to see a distant object clearly if the image of that object would be formed at his far point, which is 80 cm.
Given; object distance u = ï‚¥
Image distance v = -80 cm = - 0.8 m
The focal length and power of the required lens can be calculated by using the following formula:
The negative sign shows that the lens is a concave lens.
The power of lens = -1.25 D
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