A point object is moving along principal axis of concave mirror with uniform velocity towards pole. Initially the object is at infinite distance from pole right side of the mirror as shown. Before the object collides with mirror, the number of times a which the distance between object and its image is `40 cm` are.
.

Options

A. one time
B. two times
C. three times
D. Date insufficient

Answer

C

Explanation

As the object moves from inifinity to centre of curvature, the distance between object and image reduces from inifinity to zero.
As the object moved from centre of curvature to focus, the distance between object and image increases from zero to infinity.
As the object moved from to pole. the distance from inifinity to zero. Hence the distance object and its image shall be `40 cm` three times.