Which of the following has the most light-gathering power?
A)A telescope of 5 centimetres diameter and focal length of 50 centimetres.
B)A telescope of 6 centimetres diameter and focal length of 100 centimetres.
C)A telescope of 2 centimetres diameter and focal length of 100 centimetres.
D)A telescope of 3 centimetres diameter and focal length of 75 centimetres.

Question

Quizplus · Accepted Answer

The light-gathering power of a telescope is directly proportional to its diameter, so the larger the diameter, the more light-gathering power it has. The focal length, on the other hand, affects the magnification of the telescope. Therefore, option B has the largest diameter and hence the most light-gathering power, despite having a longer focal length.

Which of the Following Has the Most Light-Gathering Power