Question

a bright object 50 mm high stands on the axis of concave mirror of focal length 100 mm and at a distance of 300 mm from a concave mirror. How big will the image be?

Answer 1

For a concave mirror

1/f = 1/v + 1/u

-1/100 = 1/v - 1/300

1/v = -2/300

v = -150 mm

Magnification

-v/u = hi/ho

-150/300 = hi/50

hi = -25 mm

-ve sign indicates image is inverted.