Diameter of the moon is `3.5xx10^(3)km` and its distance from earth is`3.8xx10^(5)km`. It is seen by a telescope whose objectives and eyepiece have focal lengths`4` m and `10cm` respectively.The angular diameter of the image of the moon will be nearly-
(1) `5^(@)` ,(2) `10^(@)` ,(3)` 20^(@)` ,(4)`25^(@)`

Explanation

MP `= (f_(0))/(f_(e)) = - (400)/(10) = -40`
Angle subtended by the moon at the objective
`= (3.5xx 10^(3))/(3.8 xx 10^(5)) = 0.009 ` radius
Thus angular diameter of the image `=MP xx ` visual angle `=40 xx 0.009= 0.36 ` radian
`= (0.36 xx 180)/(3.14) = 21^(@)`