A simple microscope has a magnifying power of 3.0 when the image is formed at the near point (25 cm) of a normal eye. (a) What is its focal length? (b) What will be its magnifying power if the image is formed at infinity?

Answer

A, B, C

Explanation

The simple microscope has, m = 3 when image is formed at D = 25 cm
(a) `m = 1 + ((D)/(f))`
`rArr 3 =1 + ((25)/(f))`
`rArr (25)(f) = 2`
`rArr f = (25)/(2) = 12.5 cm`
(b) When the image is formed at infinity in the normal adjustment. Magnifying power `= (D)/(f) = (25)/(12.5) = 2.0`