A laser of initial energy 2.043 eV is shined into a flat glass piece of index of

Question

A laser of initial energy 2.043 eV is shined into a flat glass piece of index of refraction n = 1.432. Answer the following questions: (a) What is the initial wavelength of the laser before the photons are incident on the glass (in nm)? (b) What is the frequency of the photons inside the glass (in Hz)? (c) What is the energy of each photon while inside the glass (in eV)? (d) What is the speed of the photons inside the glass (in m/s)? (e) If the power of the laser is 50.0 mW, what is the number of photons incident on the glass each second?

Explanation / Answer

a) Energy E = h*c/lamda

2.043*1.6*10^-19 = (6.625*10^-34*3*10^8)/lamda

lamda = 608 nm

b) E = h*f = 2.043*1.6*10^-19 = 6.625*10^-34*f

frequency is f = 4.93*10^14 Hz

C) Et = Ek+Ep = ((2.043*1.6*10^-19)/1.432) + ((2.043*1.6*10^-19)/(1.432-1)) = 9.849*10^-19 J /1.6*10^-19 = 6.155 eV

D) speed is v = c/n = (3*10^8)/1.432 = 2.09*10^8 m/sec

E) P= n*E/t

n = P*t/E = P/E = 50*10^-3/(9.849*10^-19) = 5.07*10^16 photons

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