A light ray of wavelength lambda = 510. nm enters at an angle of incidence of 35.8 degrees from air into a block of plastic. Its angle of refraction is 20.1 degrees. What is the speed of the light inside the plastic?
I know I have to use Snell's law, but I keep getting the wrong answer. Can someone show me how to do it?
I know I have to use Snell's law, but I keep getting the wrong answer. Can someone show me how to do it?
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Snell's Law gives us the ratio of refractive index (μ) of the two mediums.
sin(θi) / sir(θr) = μplastic/μair
μplastic/μair = sin(35.8°) / sin(20.1°) = 1.70
The ratio [velocity of light in air] / [velocity of light in plastic] = μair / μplastic = 1 / 1.70
If we take the velocity of light in air to be the same as that in vacuum { c = 3 * 10^8 m/s }
Vplastic = 3 * 10^8/1.70 = 1.76 * 10^8 m/s
sin(θi) / sir(θr) = μplastic/μair
μplastic/μair = sin(35.8°) / sin(20.1°) = 1.70
The ratio [velocity of light in air] / [velocity of light in plastic] = μair / μplastic = 1 / 1.70
If we take the velocity of light in air to be the same as that in vacuum { c = 3 * 10^8 m/s }
Vplastic = 3 * 10^8/1.70 = 1.76 * 10^8 m/s