A 200-W infrared laser emits photons with a wavelength of 8.40 10-7 m, and a 200

Question

A 200-W infrared laser emits photons with a wavelength of 8.40 10-7 m, and a 200-W ultraviolet light emits photons with a wavelength of 1.93 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?
.......photons/s

How many ultraviolet photons are emitted per second?
.......photons/s

Explanation / Answer

The power of the infra laser light P1 = 200W the wavelength of the laser light 1 = 8.4*10^-7 m The power of the ultraviolet light P2 = 200W the wavelength of the ultraviolet 2 = 1.93*10^-7 m (a) The energy of a photon is                E = hc/ then the energy is inversely proportional to the wavelength so the ultra violet light produce greater energy. (b) The energy of a single infrared photon             E1 = hc/1                 = (6.625*10^-34 Js) (3*10^8 m/s) / 8.4*10^-7 m                  = 2.366*10^-19 J    or 1.47 eV (c) The energy of a single Ultraviolet photon             E2 = hc/2                 = (6.625*10^-34 Js) (3*10^8 m/s) / 1.93*10^-7 m                  = 1.03 *10^-18 J    or 6.44 eV (d) The number of photons emitted per sec                           n = 200/2.366*10^-19                              = 8.45*10^20 photons/sec     The number of photons emitted per sec                         n = 200/1.03*10^-18                             = 1.94*10^20 photons/sec             E2 = hc/2                 = (6.625*10^-34 Js) (3*10^8 m/s) / 1.93*10^-7 m                  = 1.03 *10^-18 J    or 6.44 eV (d) The number of photons emitted per sec                           n = 200/2.366*10^-19                              = 8.45*10^20 photons/sec     The number of photons emitted per sec                         n = 200/1.03*10^-18                             = 1.94*10^20 photons/sec

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