The focal lengths of the objective and eye`-` lens of a microscope are `1cm` and `5 cm` respectively. If the magnifying power for the relaxed eye is `45`, then the length of the tube is

Options

A. 30 cm
B. 25 cm
C. 15 cm
D. 12 cm

Answer

C

Explanation

(c ) Magnifying power,
`m_(oo)=((L_(oo)-f_(o)-f_(e))cdotD)/(f_(o)f_(e))`
`rArr45=((L_(oo)-1-5)xx25)/(1xx5)`
`rArr` The length of the tube, `L_(oo)=15 cm`