The focal length of the lensese of an astronomical telescope are 50 cm and 5 cm. The length of the telescope when the image is formed at the least distance of distinct vision is

Options

A. `45 cm`
B. `55 cm`
C. `(275)/(6) cm`
D. `(325)/(6) cm`

Answer

D

Explanation

Here, `f_(o) = 50 cm, f_(e) = 5 cm, D = 25 cm`
The length of the telescope when the image is formed at the least distance of distinct visioin is
`L = f_(o) + (f_(e)D)/(f_(e) + D) = 50+ (5 xx 25)/(5+25) = 50 = 25/6 = 325/6 cm`