An astronomical telescope of ten-fold angular magnification has a length of `44 cm`. The focal length of the objective is

Options

A. `440 cm`
B. `44 cm`
C. `40 cm`
D. `4 cm`

Answer

C

Explanation

`m = (f_(0))/(f_(e)) = 10, f_(0) = 10 f_(e), L = f_(0) + f_(e)`
`44 = 10 f_(e) + f_(e) = 11 f_(e)`
`f_(e) = 4 cm, f_(0) = 10 f_(e) = 10 xx 4 = 40 cm`