Question

You are given a spherical mirror and wish to determine its properties. You place an object on its axis, 33.3 cm in front of it, and discover that the mirror creates a virtual image located 10.9 cm from the mirror. Find the mirror's focal length.

focal length: ______cm

Calculate the mirror's radius of curvature.

radius of curvature: _____cm

If it can be determined, is the mirror concave or convex?

a.) convex

b.) cannot be determined

c.) concave

Answer 1

(A) Given the object distance u is 33.3cm and the image distance v is 10.9cm. By sign convention, u = -33.3cm. Since the image formed is virtual, v = 10.9cm. If f is the focal length of the mirror, by mirror formula,

So the focal length of the mirror is 16.2cm.

(B) The radius of curvature R of the mirror and its focal length is related by,

So the radius of the mirror is 32.4cm.

(C) Since the focal length is positive, the mirror is convex.