Question

The magnitude of magnifying power of an astronomical telescope is 5, the focal power of its eyepiece is 10 diopters. The focal power of its objective (in diopters) is

• A. $1$
• B. $2$
• C. $3$
• D. $4$

Answer 1

The correct option is B $2$

$M=5$

$P_e=10$

$\frac{1}{f_e}=10$

$f_e=\frac{1}{10}m=10cm$

$M=\frac{f_0}{f_e}=5$

$f_0=50cm$

$P=2D$