Question

The magnifying power of a telescope is $m$. If the focal length of the eye-piece is halved, then its magnifying power is :

• A. $2m$
• B. $\frac{m}{2}$
• C. $\frac{1}{2m}$
• D. $4m$

Answer 1

The correct option is A $2m$

The magnifying power $\left(m\right)$ of the reflecting telescope is $\frac{f_0}{f_e}$. If the focal length of the eye-piece is halved, then its magnifying power $m^{\prime }\left(\frac{f_0\times 2}{f_e}\right)$ is $2m$.