Question

The magnifying power of an astronomical telescope is 8 and the distance between the two lenses is 54cm. The focal length of eye lens and objective lens will be respectively

• A. 6 cm and 48 cm
• B. 48 cm and 6 cm
• C. 8 cm and 64 cm
• D. 64 cm and 8 cm

Answer 1

The correct option is A 6 cm and 48 cm

Given that $m_{\infty }=8$ and $L_{\infty }=54$
By using $|m_{\infty }|=\frac{f_o}{f_e}$ and $L_{\infty }=f_o+f_e$ we get $f_e=6cm$ and $f_o=48cm$.