A 10 mm long awl pin is placed vertically in front pin is formed at 30cm in front of the mirror. The focal length of this mirror is

Q. A 10 mm long awl pin is placed vertically in front pin is formed at 30cm in front of the mirror. The focal length of this mirror is:

A.            -30cm

B.            -20cm

C.            -40cm

D.            -60cm

Answer:-20cm