Question

An object 2 cm high is placed at a distance of 12cm from a concave mirror which produces a real image of size 4cm. Calculate the focal length of the mirror.​

Answer 1

Answer:

-24cm

Explanation:

hi/ho=-v/u

4/2=-v/12

v=-24

1/f=1/u+1/v

1/f=1/12+1/-24

1/f=-2+1/24

f=-24cm

Answer 2

-24

hi/ho = v/u

hi/ho = v/u4/2 = -v /12

hi/ho = v/u4/2 = -v /12v = -24

hi/ho = v/u4/2 = -v /12v = -241/f = 1/u+1/v

hi/ho = v/u4/2 = -v /12v = -241/f = 1/u+1/v1/f = 1/12+1/-24

hi/ho = v/u4/2 = -v /12v = -241/f = 1/u+1/v1/f = 1/12+1/-24 1/f = -2 +1/24

hi/ho = v/u4/2 = -v /12v = -241/f = 1/u+1/v1/f = 1/12+1/-24 1/f = -2 +1/24f = -24 cm