For light of wavelength 400 nm , the index of refraction of fused quartz is 1.472 , and for light of wavelength 760 nm , it is 1.452 . Determine the speeds of light for these wavelengths in fused quartz.

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Quantrex Academy · Accepted Answer

Correct answer: B. 2.04 × 10^8 m s^ -1 , 2.07 × 10^8 m s^ -1

The speed of light in a medium is given by

v = \dfrac{c}{n}

, where

c = 3 \times 10^8 \text{ m s}^{-1}

is the speed of light in vacuum and

n

is the refractive index of the medium.

For light of wavelength

400 \text{ nm}

, the refractive index is

n_1 = 1.472

.

v_1 = \dfrac{3 \times 10^8}{1.472} \approx 2.04 \times 10^8 \text{ m s}^{-1}

For light of wavelength

760 \text{ nm}

, the refractive index is

n_2 = 1.452

.

v_2 = \dfrac{3 \times 10^8}{1.452} \approx 2.07 \times 10^8 \text{ m s}^{-1}

For light of wavelength 400 nm , the index of refraction of fused...

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