A small telescope has an objective lens of focal length 140 cm and an eyepiece of focal length 5.0 cm. The magnifying power of the telescope for viewing distant objects when the final image is formed at the least distance of distinct vision 25 cm is

Question

A small telescope has an objective lens of focal length 140 cm and an eyepiece of focal length 5.0 cm. The magnifying power of the telescope for viewing distant objects when the final image is formed at the least distance of distinct vision 25 cm is (A) 33.6  (B) 66.12 (C) 22.6  (D) 11.6

Tardigrade Admin · Accepted Answer

When the final image is formed at least distance of distinct vision d, magnifying power of the telescope is m =(f0/fe)(1+(fe/d)) = (140/5)(1+(5/25)) = 33.6

Q. A small telescope has an objective lens of focal length $140 c m$ and an eyepiece of focal length $5.0 c m$ . The magnifying power of the telescope for viewing distant objects when the final image is formed at the least distance of distinct vision $25 c m$ is

$33.6$

$66.12$

$22.6$

$11.6$

When the final image is formed at least distance of distinct vision $d$ , magnifying power of the telescope is
$m = \frac{f _{0}}{f _{e}} (1 + \frac{f _{e}}{d})$
$= \frac{140}{5} (1 + \frac{5}{25}) = 33.6$

Q. A small telescope has an objective lens of focal length 140cm and an eyepiece of focal length 5.0cm. The magnifying power of the telescope for viewing distant objects when the final image is formed at the least distance of distinct vision 25cm is

33.6

66.12

22.6

11.6