Question

An object is present on the principal axis of a concave mirror at a distance 30cm from it. Focal length of mirror is 20cm.

Q. If object starts moving with `2cms^(-1)` perpendicular to principal axis above the principal axis then,
A. image moves with velocity `4cms^(-1)` below the principal axis
B. image moves with velocity `4cms^(-1)` above the principal axis
C. image moves with velocity `8cms^(-1)` below the principal axis
D. image moves with velocity `8cms^(-1)` above the principal axis

Answer 1

Correct Answer - a.
`m=-(v)/(u)=-(-60)/(-3)=-2,` so image will move twice distanc in same time as compared to object. Hence, velocity of image will be double.