Some Terms You Should Know: the Spectrum

These are some terms you will come across in your lab class dealing with the visible spectrum.
Spectrum
The order of colors produced when light is dispersed.  A rainbow is a spectrum.
Continuous Spectrum
A spectrum that contains an entire range of colors and not just separate wavelengths.
Absorption Spectrum
A spectrum that is continuous except for dark lines that appear due to material that absorbs specific wavelengths of light.
Emission Spectrum
A spectrum that is made up of separate wavelengths on a dark bakground due to material that emits specific wavelengths of light.
Diffraction Grating
A grid with small openings that can be used to separate light into its component wavelengths.
Doppler Shift
The observed change in a wavelength that occurs when a wave source is moving toward you or away from you.
Hubble Constant
The ratio of a galaxy's recessional velocity (how fast it is moving away from Earth) to its distance from Earth.  This constant can be used to estimate the age of the universe.

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 This page was last updated on 8 March 1998
and is © 1998 by Jim McDonald.