How does the light-gathering power of a 40 cm telescope compare to that of a 20 cm telescope?
A)They are the same
B)2 times as great
C)4 times as great
D)8 times as great

Question

Quizplus · Accepted Answer

The light-gathering power of a telescope is directly proportional to the area of its objective lens or mirror. The area of a 40 cm telescope is four times that of a 20 cm telescope because the area of a circle is proportional to the square of its radius (πr²). Therefore, the 40 cm telescope has four times the light-gathering power of the 20 cm telescope.

How Does the Light-Gathering Power of a 40 Cm Telescope