Many fortunate amateur astronomers have telescopes with primary mirrors 20 cm in diameter.The recently built Keck telescopes on Hawaii have mirrors 10 m in diameter.How much more light is collected by one of the Keck telescopes compared with the amateur's telescope?
A) 2500 times more
B) 50 times more
C) About 7 times more
D) 2 times less

Question

Quizplus · Accepted Answer

The amount of light collected by a telescope is proportional to the area of its objective lens, which is proportional to the square of its diameter. Therefore, the Keck telescope has (10/0.20)^2 = 2500 times more light-collecting area than the amateur's telescope.

Many Fortunate Amateur Astronomers Have Telescopes with Primary Mirrors 20