A camera has a converging lens with a focal length of 56 mm. If the f-number is 2.8, what is the diameter of the lens (in mm)?
A) 10
B) 31
C) 0.50
D) 20
E) 50

Question

Quizplus · Accepted Answer

The formula for f-number is: f-number = focal length / diameter of lens
We are given the focal length (f) = 56 mm and the f-number = 2.8
Plugging in the values, we get:
2.8 = 56 / diameter of lens
Solving for diameter of lens:
diameter of lens = 56 / 2.8 = 20 mm
Therefore, the answer is D.

A Camera Has a Converging Lens with a Focal Length