102: Solar Spectrum

The sun’s core emits a continuous spectrum of light. However, the gas atoms in the sun’s “atmosphere” are capable of absorbing some of this light. Thanks to the discrete energy levels in gas atoms, these gas atoms can only absorb photons of certain energies (and since E=hc/λ, photons of certain wavelengths) that match the energy gaps in the energy levels of the gas atoms (|E2-E1|= hc/λ), resulting in dark lines in the solar spectrum at those wavelengths.


Out of curiosity, I tried to match the absorption lines in my video to those published on the internet (see http://en.wikipedia.org/wiki/Sunlight). With a little confidence, I think four of the more prominent dark lines (labelled C, D, E and F) in the spectrum are due to absorption by Sodium, Iron, Hydrogen and Iron atoms in the Sun’s atmosphere.


It came as a surprise to me that the absorption lines of the solar spectrum can be viewed directly with the naked eyes using a grating. Although the video camera tends to over exposure the image (thus resulting in the absorption lines being washed out), the dark lines are clearly visible momentarily when the camera was in the midst of “correcting” the exposure.

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