The relative aperture or f -stop ( f ) for a camera lens is inversely proportional to the diameter of the aperture ( d ). An f -stop of 2 corresponds to an aperture diameter of 40 millimeters for the lens on an automatic camera. Find the equation that relates f -stop and diameter.

Question

Quizplus · Accepted Answer

We know that f is inversely proportional to d, so we can write the equation as f = k/d where k is the constant of proportionality. To solve for k, we can use the given information that an f-stop of 2 corresponds to an aperture diameter of 40 millimeters. Plugging in f=2 and d=40, we get:

2 = k/40

k = 80

So our equation is:

f = 80/d

And the correct choice is C.

The Relative Aperture or F -Stop ( F ) for a Camera