The Blu-ray Player technology is better than the DVD, in that it uses blue last

Question

The Blu-ray Player technology is better than the DVD, in that it uses blue last light instead of orange/red. The laser can be more precisely focused; the grooves on the disk can be smaller, and therefore closer together. This makes it possible to it more information. Lets say the wavelength of Blu-ray light is 425 nm. Calculate the frequency of one photon of this light. What is this photon's energy? What is the energy of 1 mole Blu-ray photons? How many photons will strike the surface of the disk if you are watching an hour and a half long movie? I found the rate of consumption to be .25J/s

Explanation / Answer

a)
f = c/wavelength
= (3*10^8)/ (425*10^-9)
= 7.06*10^14 Hz

b)
E = h*f
= (6.626*10^-34)*(7.06*10^14)
=4.68*10^-19 J

c)
energy of 1 mol = 6.022*10^23 * 4.68*10^-19
=2.82*10^5 J

d)
t = 1 and half hour = 5400 s
Energy hitting = 0.25 J/s * 5400 s = 1350 J

number of photon = energy hitting/ energy of 1 photon
= 1350 / (4.68*10^-19)
= 2.88*10^21 photons

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