A monochromatic ray of light (f=5.09 x 10^14 Hz) travels from air into sodium chloride. Calculate the speed of light in sodium chloride.

1.95 * 10^8 ms-1

Explanation:

Let us recall that;

Refractive index (n) = Frequency of light in air/Frequency of light in another medium

If Frequency of light in air = 5.09 x 10^14 Hz

Refractive index of sodium chloride = 1.54

Then;

Frequency of light in sodium chloride =  Frequency of light in air/Refractive index of sodium chloride

Therefore;

Frequency of light in sodium chloride =  5.09 x 10^14 Hz/1.54

Frequency of light in sodium chloride =  3.31 x 10^14 Hz

So;

n= Frequency of light in air/Frequency of light in sodium chloride = Speed of light in air/speed of light in sodium chloride

speed of light in sodium chloride = Frequency of light in sodium chloride * Speed of light in air/Frequency of light in air

speed of light in sodium chloride = 3.31 x 10^14 Hz * 3 * 10^8 ms-1/5.09 x 10^14 Hz

speed of light in sodium chloride = 1.95 * 10^8 ms-1

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