Question

A lady cannot see object closer than 40 cm from the left eye and closer than 100 cm from the right eye. on mountaineering trip, she lost from her team. She tries to make an astronomical telescope from her reading glass. (a) Which glass should be used as the eyepiece? (B) what is the magnification of relaxed eye?

Answer 1

(a) Right eye glass be used as eyepiece.
$\frac{1}{f_{Left}}=\frac{1}{25}-\frac{1}{40}=\frac{1.5}{100}or{f}_{Left}=\frac{100}{1.5}cm\frac{1}{f_{right}}=\frac{1}{25}-\frac{1}{100}=\frac{3}{100}or{f}_{right}=\frac{100}{3}cm$.
In telescope eyepiece of shorter focal length is used.
(B) $M=\frac{f_o}{f_e}=2$