Glossary

This glossary covers words that you will come across on this website.

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Click one of the letters above to be taken to a page of all terms beginning with that letter.

Dispersion

1. The splitting of light into its separate colours by means of a prism or diffraction grating.

2. A phenomenom where by electromagnetic waves of different frequencies travel at different speeds through certain medium such as ionized gases (plasmas). ( note: all electromagnetic waves should travel at the speed of light [3*10^8]) Most interstellar matter is ionized hydrogen, and is therefore dispersive.

Doppler Effect

A change in the observed frequency of a wave, as of sound or light, occurring when the source and observer are in motion relative to each other, with the frequency increasing when the source and observer approach each other and decreasing when they move apart. The motion of the source causes a real shift in frequency of the wave, while the motion of the observer produces only an apparent shift in frequency. Also called Doppler shift.