Question

A convex mirror has a focal length of 20 centimeters. An object 8 centimeters high is placed 11 centimeters in front of the mirror.

f. Calculate the distance of the image from the mirror.   (cm)

g. Calculate the height of the image. (cm)

h. Calculate the magnification.

Answer 1

1/u + 1/v = 1/f
For convex mirror f is -ve.
1/11 + 1/v = 1/(-20)
v = -7.1 cm
distance of image from mirror = 7.1 cm, -ve sign indiactes virtual image.

height of image = height of object ( magnitude of v/u)
                         = 8*7.1/11
                         = 5.2 cm

Magnification = -(v/u)
                     = - (-7.1/11)
                       = + 0.64 (+ve sign indicates erect image)