A Keplerian refracting telescope is used to look at craters on the moon.The objective focal length of the telescope is 92 cm and the distance between the objective and eyepiece lenses is 97 cm.The diameter of the objective is 25 cm.What is the focal length of the eyepiece?
A)5.0 cm
B)2.5 cm
C)15 cm
D)10 cm
E)20 cm

Question

Quizplus · Accepted Answer

The focal length of the eyepiece can be found using the lens equation for a telescope, where the distance between the objective and eyepiece lenses equals the sum of their focal lengths: $f_o + f_e = d$. Given $f_o = 92$ cm and $d = 97$ cm, solving for $f_e$ gives $f_e = d - f_o = 97 - 92 = 5$ cm.

A Keplerian Refracting Telescope Is Used to Look at Craters