Question

There is a telescope of magnifying power $5$ and tube length $60cm$ . What is the focal length of its eye piece?

• A. $30cm$
• B. $10cm$
• C. $40cm$
• D. $20cm$

Answer 1

Answer: (B)

$m=\frac{f_0}{f_e}$
$5=\frac{f_0}{f_e}$
$f_0=5f_e$
$f_0+f_e=60$
$6f_e=60$
$f_e=10$ .