A Galilean telescope of `10`-fold magnification has the length of `45 cm` when adjusted to infinity. Determine :
(a) the focal lengths of the telescope's objective and ocular,
(b) by what distance the ocualr should be displaced to adjust the telescope to the distance of `50 m.`

Options

A. 50 cm, 5cm
B. `50cm, -5cm`
C. `(450)/(11)cm, (45)/(11)cm`
D. `(450)/(11)cm, (-45)/(11)cm`

Answer

B

Explanation

For Galilean telescope eyepiece is diverging and final image is erect.
`f_(0)+(f_(0))=45cm`
`-f_(0)//f_(0)=10`
`rArrf_(0)=50cm, f_(e)=-5cm`