A projector lens is needed to form an image on a screen 6 times the size of its corresponding object.The screen is located 8.65 m from the lens.What is the required focal length of the lens?
A)1.44 m
B)7.41 m
C)1.24 m
D)0.721 m
E)1.73 m

Question

Quizplus · Accepted Answer

The magnification (m) is given by the ratio of the image distance (v) to the object distance (u), m = v/u. Since the image is 6 times the size of the object, m = 6. The lens equation is 1/f = 1/v + 1/u. Rearranging for u gives u = v/6. Substituting u into the lens equation and solving for f with v = 8.65 m gives f ≈ 1.24 m.

A Projector Lens Is Needed to Form an Image on a Screen