Astronomy 122
Some Mid-term Exam I Equations
January 13, 2015, jeb
For Electromagnetic Radiation
wavelength x frequency = velocity = 300,000 km/sec |
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frequency = velocity/wavelength = 300,000 km/sec/wavelength |
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For example, for visible light (0.5 μ m)
f = 3 x 10^{5} km/sec/0.5 microns
= 3 x 10^{5} x 10^{3} m/sec/0.5 x 10^{-6}m
= 6 x 10^{14} /sec
= 6 x 10^{14} Hertz
where E is energy (in Joules)
h is Planck's constant
(h = 6.63 x 10 ^{-34}Joule seconds)
and f is frequency in 1/sec, or Hz.
Photon energies are very small
f = 6 x 10^{14} Hertz
So, E = 4 x 10^{-19} Joules