Question

An astronomical telescope has an eye piece of focal length 5 cm. If magnification produced is 14 in normal adjustment, then calculate the length of the telescope

Answer 1

Given focal length of eye piece f₁ = 5 cm

Magnification m = 14

Also we know

m = (f₀/f₁)

f₀ = 14× 5 = 70 cm

Now the distance between the focuses of eye piece and objective = length of the telescope = f₀ - f₁ = 70 - 5 = 65 cm