. A camera with a 50.0-mm focal length lens is being used to photograph a person standing 3.00 m away. (a) How far from the lens must the film be

Explanation:

Using the lens formula 1/f = 1/u + 1/v

f = focal length of the lens

u = object distance

v = image distance

Given focal length f = 50.0mm = 50/1000 = 0.05m

Note that a camera uses a convex lens and the focal length of a convex lens is positive.

object distance u = 5.00m

To know how far from the lens must the film be, we need to calculate the image distance v.

from the formula above;

1/v = 1/f - 1/u

1/v = 1/0.05 - 1/3

1/v = 20-0.33

1/v = 19.67

v = 1/19.67

v = 0.051m

Hence, the film must be 0.051 m away from the lens