Astronomy 122
Some Mid-term Exam I Equations
October 4, 2016
Astronomy 122
Prof. J. Brau
For Electromagnetic Radiation
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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 105 km/sec/0.5 microns
= 3 x 105 x 103 m/sec/0.5 x 10-6m
= 6 x 1014 /sec
= 6 x 1014 Hertz
where E is energy (in Joules)
h is Planck's constant
(h = 6.63 x 10 -34Joule seconds)
and f is frequency in 1/sec, or Hz.
Photon energies are very small
f = 6 x 1014 Hertz
So, E = 4 x 10-19 Joules