Question

The magnifying power of an astronomical telescope is 8 and the distance between the two lenses is 54cm. The focal length of eye lens and objective lens will be respectively

• A. 6 cm and 48 cm
• B. 48 cm and 6 cm
• C. 8 cm and 64 cm
• D. 64 cm and 8 cm

Answer 1

Answer: (A)

6 cm and 48 cm

Answer 2

Given that $L _ { \infty } = 54$

By using $\left| m _ { \infty } \right| = \frac { f _ { o } } { f _ { e } }$ and $L _ { \infty } = f _ { o } + f _ { e }$ we get $f _ { o } = 6 \mathrm {~cm}$

and $f _ { e } = 48 \mathrm {~cm}$.