Question

an object is placed at a distance of 30 cm from a concave mirror and its real image is formed at a distance of 30 cm from the mirror the focal length of the mirror is​

Answer 1

Answer:

Using convention used for mirrors

u = - 30cm

v = - 30cm (real image)

From mirror formula

1/u + 1/v = 1/f

f = uv/(u+v) = (-30*-30)/(-30-30) = - 15cm

Focal length of the mirror is

f = - 15cm (minus mean concave mirror)

Answer 2

Answer: u= -30 cm

f= -20 cm

By using mirror formula,

1/v + 1/u = 1/f

1/v + 1/-30 = 1/-20

v= -60 cm

negative sign indicates that image is in front of the mirror

Therefore,

The distance between image and object = 60–30 = 30cm

Explanation: