To get three images of a single object, one should have two plane mirrors at an angle of 60°.

• A. 60°
• B. 90°
• C. 120°
• D. 30°

To determine the angle needed between two plane mirrors to create three images of a single object, we can use the formula related to the number of images formed:

Formula for Number of Images

The number of images (N) formed by two mirrors at an angle (θ) is given by:

N = (360° / θ) - 1

Calculating for Three Images

We want to find the angle that results in three images:

3 = (360° / θ) - 1

Rearranging gives:

4 = 360° / θ

Thus, we find:

θ = 360° / 4 = 90°

Correct Answer

The angle between the two mirrors should be 90° to obtain three images of the object. Therefore, the correct option is:

• B. 90°