A telescope has focal length of objective and eye-piece as 200 cm and 5 cm respectively. What is magnification of telescope?

In relaxed eye state of telescope or when final image is formed at infinity, the magnification of telescope is given by $|M|=\frac{f_o}{f_e}$ where $\begin{aligned} f_o & =\text { focal length of objective }=200 \mathrm{~cm} \\ f_e & =\text { focal length of eye-piece }=5 \mathrm{~cm}\end{aligned}$ Hence, $|M|=\frac{200}{5}=40$ $|M|=\frac{200}{5}=40$ Note : The aperture of the objective lens is kept large so that more and more rays coming from the heavenly body may enter the telescope and a bright image is formed by the objective lens. The aperture of the eye lens is kept comparatively small so that all the rays may enter the eye.