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

Q. 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

A.            – 30 cm

B.            30 cm

C.            – 15 cm

D.            +15 cm

Answer: – 15 cm