(a) Calculate the wavelength of light in vacuum that has a frequency of 5.7e12 H

Question

(a) Calculate the wavelength of light in vacuum that has a frequency of 5.7e12 Hz. ______m (b) What is its wavelength in ethyl alcohol? (The index of refraction of ethyl alcohol is 1.361.) ______m (c) Calculate the energy of one photon of such light in vacuum. Express the answer in electron volts. ______ eV (d) What is the properties of and effect on the energy of the photon when it enters the ethyl alcohol? (Select all that apply.) [ ] the energy does not change [ ] the energy goes up [ ] the energy is inversely proportional to the frequency [ ] the energy goes down [ ] the energy is proportional to the frequency [ ] the energy is not proportional to the frequency

Explanation / Answer

a)wavelength = c/f = (3*10^8 )/ (9.8*10^12)= 0.306 * 10^-4 m =30.6 micrometres

b)wavelength in ethyl alcohol= 30.6*1.361=41.646 micrometres

c)energy=

hc/lambda

= (6.625 * 10^-34 * 3 * 10^8)/30.6 * 10^-6

=0.6495 * 10^-20 joules = (0.6495 * 10^-20)/(1.6*10^-19)=0.406 * 10^-1=0.0406 eV

d) the energy is proprotional to frequency

the energy does not change

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