A 200-W infrared laser emits photons with a wavelength of 7.00 X 10^-7 m, and a

Question

A 200-W infrared laser emits photons with a wavelength of 7.00 X 10^-7 m, and a 200-W ultraviolet light emits photons with a wavelength of 3.64 X 10^-7 m (a) Which has greater energy, a single infrared photon or a single ultraviolet photon? a single infrared photon a single ultraviolet photon (b) What is the energy of a single infrared photon? J What is the energy of a single ultraviolet photon? J (c) How many infrared photons are emitted per second? E photons/s How many ultraviolet photons are emitted per second? photons/s

Explanation / Answer

a) for infrared

E = hc/lambda = 1240/(7.0E-7*10^9)= 1.77 eV

for ultraviolet

E = hc/lambda = 1240/(3.64E-7*10^9)= 3.41 eV

so ultraviolet

b)

E infrared = 1.77*1.6E-19= 2.93E-19 J

Eultraviolet = 3.41*1.6E-19= 5.46E-19 J

c)
N infrared = 200/2.93E-19= 6.83E20

Nultraviolet = 200/5.46E-19 = 3.66E20

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