A camera lens has a focal length of 50.0 mm and an aperture setting of f/4.00. What is the diameter of the aperture of this lens?
A) 200 mm
B) 12.5 mm
C) 25.0 mm
D) 35.4 mm
E) 10.1 mm

Question

Quizplus · Accepted Answer

The diameter of the aperture can be calculated using the formula for the f-number: $f$-number = focal length / diameter of the aperture. Rearranging for the diameter gives: diameter = focal length / $f$-number = 50.0 mm / 4.00 = 12.5 mm.

A Camera Lens Has a Focal Length of 50