PHYSICS

JAMB 2006 - Question 33

Physics 2006 JAMB Past Questions - Question 33: A person can focus objects when they lie beyond 75cm from his eyes. The focal length of the lens required to reduce his least distance of distinct vision to 25 cm is

Choose the correct answers from the options given.
A person can focus objects when they lie beyond 75cm from his eyes. The focal length of the lens required to reduce his least distance of distinct vision to 25 cm is
A:
B:
C:
D:
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Correct Answer

B

Explanation

The least distance of distinct vision required = 25 cm.
∴ for the person to see an object clearly at 25 cm from the eye, the image must be formed at 75 cm on the same side of lens, at his near point.
∴ U = 25 cm; V = -75 cm (image should be virtual)
thus (1)/f = (1)/v +(1)/u
= (1)/75 + (1)/25
=(-1 + 3)/75 = (2)/75
∴f = (75)/2 = 37.50