Question

Focal length of a concave mirror is 10 cm. Draw a ray diagram to show the image formation of the mirror when the object is placed at 20 cm.

Answer 1

Explanation:

Given:

Focal length of concave mirror, f = -20 cm

Distance of object from the mirror, u = -10 cm

use formula, 1/v + 1/u = 1/f  

or, 1/v = 1/f - 1/u  

or, 1/v = 1/-20 - 1/-10  

or, 1/v = -1/20 + 1/10 = 1/20  

or, v = +20cm  

hence, image position is the 20cm right side from the pole of the concave mirror as shown in the diagram. The image is straight and bigger than the object.