Optics Question 428

Question: A simple magnifying lens is used in such a way that an image is formed at 25 cm away from the eye. In order to have 10 times magnification, the focal length of the lens should be

[MP PET 1990]

Options:

A) 5 cm

B) 2 cm

C) 25 mm

D) 0.1 mm

Show Answer

Answer:

Correct Answer: C

Solution:

m = $ 1+\frac{D}{f _{e}} $

Therefore $ 10=1+\frac{25}{f _{e}} $

Therefore $ f _{e}=\frac{25}{9} $ $\tilde{}$ $ 25mm $



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