QQuestion
For the same angle of incidence, the angles of refraction in three different media A, B and C are 30°, 45° and 60° respectively. In which medium is the speed of light minimum and why? [3]
✓Answer
For the same angle of incidence,
Angle of refraction in medium A = 30°
Angle of refraction in medium B = 45°
Angle of refraction in medium C = 60°
According to Snell’s law,
μ = \frac{\sin\text{i}}{\sin\text{r}}
Since the angle of incidence i is the same for all three media, the medium having the smallest angle of refraction has the highest refractive index.
Therefore,
μA > μB > μC
Also, v = \frac{\text{c}}{\text{μ}}
Thus, greater refractive index means lower speed of light.
Hence, the speed of light is minimum in medium A because it has the smallest angle of refraction (30°) and therefore the highest refractive index.
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