Question

An object at a distance of 30 cm from a concave mirror gets its image at the same point. The
focal length of the mirror is:​

Answer 1

Answer:

u=30 cm

f=20 cm

v=?

→mirror formula←

1/f=1/v+1/u

for concave mirror f is in -ve

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

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

1/v=-3+2/60

1/v=-1/60

v=-60 cm

hence image is formed at 60 cm at the same side of the mirror as that of the object

hope this helps

Answer 2

Answer:

Object distance , u=+30cm and image distance v=+30cm

If f be the focal length, 1/f=1/u+1/v=1/30+1/30=1/15 or f=15cm

Explanation:

Hope it helped u