Question

Violet light and red light travel through air and strike a block of plastic at the same angle of incidence. The angle of refraction is 30.400 degrees for the violet light and 31.200 degrees for the red light. The index of refraction for violet light in plastic is greater than that for red light by 0.0400. Delaying any rounding off of calculations until the very end, find the index of refraction for violet light in plastic.

Answer 1

Solution:

Using snell's law,

=> n1 sin i = n2 sin r ...............(i)

given index of refraction of voilet light is greater than red light by 0.0400 so,

n2 = n1 + 0.04

using equation 1,

n1 x sin 31.2 = (n1+0.04) 30.4 (n1 is refractive index for red)

=> n1 x 0.518 = (n1 + 0.04 ) x 0.506

=> n1 x 0.518 = n1 x 0.506 + 0.04 x 0.506

=> n1 x 0.012 = 0.04 x 0.506

=> n1 = 1.69 (approx)

So refractive index for voilet light is 1.69 + 0.04 => 1.73

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