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What is the Energy of the Photons Emitted by the Hydrogen 21cm Transition?

-- | June 22, 2014

Question: What is the typical amplitude in volts (milli, micro, or otherwise) of radio waves around the 1420 MHz frequency, received by earth stations? — Pete

Answer: The energy contained in a photon emitted at a particular wavelength is determined by the atomic or molecular transition that generates the photon. In the case of the 1420 MHz hydrogen hyperfine transition, the difference in energy between the hyperfine energy states that produces the 1420 MHz frequency is 5.87433 x 10^(-6) electron volts.

Jeff Mangum

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