The angular magnification of a telescope is `300` What should be the diameter of the objective, if our eyes at the eye ring, are just able to collect all the light refracted from the objective. Take diameter of pupil of eye `= 3mm`.

Answer

`90 cm`

Explanation

Here, `m = 300, D = ?, d = 3mm = 0.3 cm`.

`m = (f_(0))/(f_(e)) = (D// theta)/(d// theta) = (D)/(d)`
`:. D = m xx d = 300 xx 0.3 = 90 cm`