An object is in front of a concave spherical mirror,and its image is 4.0 cm behind the mirror.If the focal length of the mirror has a magnitude of 5.0 cm,where is the object?
A)2.2 cm in front of the mirror
B)2.2 cm behind the mirror
C)9.0 cm in front of the mirror
D)1.0 cm behind the mirror

Question

Quizplus · Accepted Answer

The image is behind the mirror, so the object must be in front of the mirror. The focal length is positive, so the mirror is concave. Using the thin lens equation, 1/f = 1/do + 1/di, we can solve for the object distance, do: do = 1/(1/f - 1/di) = 1/(1/5 cm - 1/4 cm) = 2.2 cm.

An Object Is in Front of a Concave Spherical Mirror,and