Question

The maximum angular magnification produced by an astronomical telescope is $30$. If the focal length of the eyepiece is $12.5\text{cm}$, then find the minimum angular magnification produced by it.

• A. $20$
• B. $15$
• C. $25$
• D. $10$

Answer 1

The correct option is A $20$

The relation between maximum and minimum angular magnification achieved by the astronomical telescope can be given as,

$m_{\text{max}}=m_{\text{min}}(1+\frac{f_e}{D})$

$\Rightarrow 30=m_{\text{min}}(1+\frac{12.5}{25})$

$\Rightarrow m_{\text{min}}=20$

Hence, option $\left(A\right)$ is the correct answer.