An astronomical telescope consisting of an objective of focal length `60cm` and eye-piece of focal length `3 cm` is focused on the moon so that the final image is formed at least distance vision, i.e. `25 cm` from the eye-piece piece. Assuming the angular diameter of moon as `1//2^(@)` at the objective, calculate (a) angular size and (b) linear size of image seen through the telescope.

Explanation

As final image is at least distance of distinct vision,
`|M|=f_(0)/f_(e)[1 + f_(e)/D]=60/3[1 + 3/25]=22.4`
Now as by defination `M=(theta/theta_(0))`, so the angular size of image
`theta=Mxxtheta_(0)=22.4xx[1/2]^(@)=11.2^@`
`=pi/180xx11.2=0.2` rad
And if the size of final image whic is at least distance of distinct vision `theta=(I/25)`
i.e., `I=25xxtheta=25xx0.2=5cm`