Physics
A ray of light is incident normally on a face of an equilateral prism. The ray gets totally reflected at the second refracting surface. The total deviation produced in the path of the ray is:
- 30°
- 60°
- 90°
- 120°
Answer
60°
Reason — As, the ray is normally incident on face AB so it passes undeviated. Angle of incidence on face AC is 60˚. The reflected ray is incident normally on face BC and passes undeviated.
Now, from the above diagram,
∠NRS = 60˚
∴ ∠SRC = 30˚
∠ARQ = 30˚
∴ ∠CRT = 30˚
RT is the original path of the incident ray.
So, total deviation = ∠SRT = 30˚ + 30˚ = 60˚
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