Question

A telescope has an objective lens of focal length 150 cm and an eyepiece of focal length 5 cm. Calculate its magnifying power in normal adjustment and the distance of the image formed by the objective.

Answer 1

Given, f₀ = 150 cm

f_e = 5cm

In normal adjustment,

`m = -f_0/f_e`

= `-150/5`

= −30

For objective lens,

`1/f_0 = 1/v_0 - 1/u_0`

`1/150 = 1/v_0 - 1/infty`   ...[∵ u₀ = ∞, as object is at infinity]

v₀ = 150 cm