A man at the back of a crowd watches a parade by holding a plane mirror just above his head. The parade passes 6 metres behinde his head and the mirror is 0.25m in front of the man. How far does the image in the mirror appear to be from the man?
A
6.50m
B
6.25m
C
6.00m
D
5.75m
E
5.50m
Verified Correct Answer: A.
Physical Principles & Numerical Solution
In a plane mirror, the image is formed as far behind the mirror as the object is in front of it.
- The parade (object) is 6 m behind the man’s head.
- The mirror is held 0.25 m in front of the man.
So, the total distance from the parade to the mirror is:
6 m + 0.25 m = 6.25 m.
The image will therefore appear 6.25 m behind the mirror.
The man is looking into the mirror, so the distance from the man to the image is:
Distance from man to mirror + Distance from mirror to image
= 0.25 m + 6.25 m
= 6.50 m
Thus, the image of the parade appears to be 6.50 metres from the man.
Source: Myschool Past Questions Archive (Record #42742)