Laser Light Violet
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Calculate the energy of a photon of wavelength?
Calculate the energy of a photon of wavelength 3.4 µm with that of wavelength 0.157 nm.
a) 3.4 µm photon
J
b) 0.157 nm photon
J
a) An argon ion laser emits light at 489 nm. What is the frequency of this radiation?
b) Is this emission in the visible spectrum?
Yes or No
c) If yes, what color is it?
violet
yellow
orange
red
green
Not in the visible spectrum
The energy (E) of a photon is related to its frequency f by Planck's constant, h,
by: E = hf, where h = 6.625 * 10**-34 joule-seconds. The frequency is inversely
related to its wavelength w by: f = c/w, where c is the speed of light, 300 million
meters per second. So E is related to the wavelength w by: E = hc/w. Since h
and c are constant, their product hc is constant, 19.875 * 10**-26 joule-meters.
So the energy of the 3.4 µm photon (3.4 * 10**-6 meter) is found by:
E = (19.875 * 10**-26)/(3.4 * 10**-6) = 5.845 * 10**-20 joule.
(b) The energy of the 0.157 nm photon, or 1.57 * 10**-10 meter is found by:
E = (1.9875 * 10**-25)/(1.57 * 10**-10) = 1.266 * 10**-15 joule.
Regarding the argon laser, the frequency f is found by: f = c/w, where w is the
wavelength. So f = (3.0 * 10**8)/(4.89 * 10**-7) = 6.135 * 10**14 waves/sec. or Hz.
This light is visible, blue-green in color, so green is the closest answer.
Hope this answers your questions.
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