Question

In normal adjustment, for a refracting telescope, the distance between objective and eye piece lens is 1.00 m. If the magnifying power of the telescope is 19, find the focal length of the objective and the eyepiece lens.

Answer 1

Given f₀ + f_e = 100 cm   ...(i)

and magnifying power = `f_0/f_e = 19`

⇒ f₀ = 19f_e

From eqn (i), 19f_e + f_e = 100

⇒ f_e = 5 cm 

So f₀ = 95 cm