A small refracting "spyglass" telescope has an objective with a focal length of about 30 inches.The world's largest refracting telescope at Yerkes Observatory has an objective with a focal length of 63.5 feet.If they both use the same eyepiece,how much larger is the image with Yerkes than with the spyglass?
A) about twice
B) about 16 times
C) about 25 times
D) about 625 times

Question

Quizplus · Accepted Answer

The ratio of the size of the image produced by the Yerkes telescope to the size of the image produced by the spyglass telescope can be found using the formula:

size of image ∝ focal length of objective

Since they use the same eyepiece, the size of the image is proportional to the focal length of the objective.

Therefore,

size of image with Yerkes telescope / size of image with spyglass telescope = focal length of Yerkes objective / focal length of spyglass objective

Substituting the given values, we get:

size of image with Yerkes telescope / size of image with spyglass telescope = 63.5 feet / 30 inches

= (63.5 x 12) inches / 30 inches

= 25.4 inches / inch

So, the size of the image produced by the Yerkes telescope is about 25 times larger than the size of the image produced by the spyglass telescope.

Therefore, the correct answer is (C) about 25 times.

A Small Refracting "Spyglass" Telescope Has an Objective with a Focal