In the diagram above, an incident ray AY makes an angle of 30o with the normal XY. If the mirror is rotated anticlockwise about Y through an angle of 20o, while AY is fixed, what angle will the reflected ray now make with the incident ray?
Attached Figure / Diagram
A
70o
B
80o
C
100o
D
120o
Verified Correct Answer: C.
Physical Principles & Numerical Solution
The reflected ray will rotate through angle 2 x 20º = 40º
The reflected ray will now make angle 30º + 30º + 40º = 100º with the incident ray(30º + 30º since i = r)
Source: Myschool Past Questions Archive (Record #33810)