Spectra

Visible light is one small portion of the electromagnetic spectrum When light is refracted (bent), the light is split into its individual wavelengths Each wavelength appears as a different color The entire range of colors makes up a spectrum We can refract light with an instrument called a spectroscope

Types Of Spectra

1. Continuous Formation- when a solid, liquid, or high pressure gas is heated to a high temperature, it emits all wavelengths Appearance- a full rainbow Image from http://www.euhou.net INCANDESCENT BULB

2. Bright-line emission Formation- when a low pressure or low density gas is heated, the electrons get excited and jump energy levels. Energy is emitted at specific wavelengths. Each gas has its own distinct pattern Appearance- a couple thin lines of color http://mooni.fccj.org/~ethall/spectra/spectra.htm

3. Continuous with bright lines Formation--Common in fluorescent bulbs Appearance-a full rainbow in the background with a few especially bright lines http://www.euhou.net FLOURESCENT BULB

4. Absorption/ Continuous with Dark lines Formation-caused when cooler atoms are between the light source and the observer and remove (absorb) certain wavelengths of light. Common in stars Modified from www.uwplatt.edu STAR FILTERED LIGHT Light source Cool gas You Appearance-as a chunk of a rainbow or a rainbow with black lines through it

IMPORTANCE Scientists can determine the composition of stars by matching the dark line pattern in the star’s spectra with the bright line emission patterns of known gasses http://www.chem1.com/acad/webtext/atoms/atpt-3.html