Q2 of 79 Page 380

The wavelength of sodium light in air is 589 nm. (a) Find its frequency in air. (b) Find its wavelength in water (refractive index = 133). (c) Find its frequency in water. (d) Find its speed in water.

Given wavelength of sodium light in air is

(a)Therefore, the frequency is .


(b) Wavelength of light in a medium of refractive index is given by .


Therefore, the wavelength of sodium light in water is


(c)Frequency of light doesn’t change due to a change in medium as both the speed of light and the wavelength of light are reduced by the same amount(). So the frequency is .


(d)The speed of light in a medium is given by


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