When a girl moves towards a plane mirror at a speed of 4.0m/s, the distance between the girl & her image reduces at a speed of
A
2 m/s
B
4 m/s
C
8 m/s
D
12 m/s
Verified Correct Answer: C.
Physical Principles & Numerical Solution
The image in a plane mirror is as far behind the mirror as the girl is in front of it.
If she is at a distance d from the mirror, her image is also d behind it.
Total distance between girl and image = 2d.
v = \(\frac{\text{d}}{\text{t}}\) or v ∝ d
d = x, v = 4m/s
d = 2x, v = ? (girl & image)
v = 2 x 4 = 8m/s.
Source: Myschool Past Questions Archive (Record #55582)