Question

An object 1 cm tall is placed 30 cm in front of a convex mirror of focal length 20 cm. Find the size and position of the image formed by the convex mirror.

Answer 1

u= -30cm

f= +20cm

ho= +1cm

Using mirror formula,

1/v+1/u=1/f

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

1/v-1/30=1/20

1/v=1/20+1/30

1/v=3+2/60

1/v=5/60=1/12

=>v= +12cm

Therefore, the image will be formed at a distance of 12cm behind the mirror.

m= -v/u

m= -12/-30

m= +0.4

m=hi/ho

0.4=hi/ho

0.4=hi/1

=>hi= +0.4cm

Therefore, the image formed is diminished in size.