An object moves axially at 3 cm/s. At an instant its real image in a concave mirror moves at 12 cm/s in the opposite direction, and object-image separation is 30 cm. Find |f| in centimetres.
An object moves axially at 3 cm/s. At an instant its real image in a concave mirror moves at 12 cm/s in the opposite direction, and object-image separation is 30 cm. Find |f| in centimetres.