AS101 Lecture Notes - Lecture 3: Black-Body Radiation, Photon
Document Summary
To understand how to analyze a spectrum, began with a incandescent simple light bulb. The hot filament emits blackbody radiation, which forms a continuous spectrum. An absorption spectrum results when radiation cold gas. In this case you can imagine that the light bulb is surrounded by a cool cloud of gas. Atoms in the gas absorb photons of certain wavelengths, which positions as dark absorption lines. An emission spectrum is produced by photons emitted by an excited gas. You could see emission lines by turning your telescope aside so that photons from the bright bulb did not enter the telescope. The photons you would see would be emitted by the excited atoms near the bulb. The spectrum of a star is an absorption spectrum. The denser layers of the photosphere emit black body radiation. Gases in the atmosphere of the star absorb their specific wavelengths and form dark absorption lines in the spectrum.
