Astronomical Spectra What about solid objects? When atoms get really, really close together where they are pretty much solid, or thick enough that they are pretty close to solid, then the levels of the atoms get really screwed up. They are sort of mushed around so that they aren't too picky about the type of light that they'll absorb - they'll absorb longer and shorter wavelength light and even longer and even shorter as the material gets denser and thicker. A solid can absorb pretty much all wavelengths of light, while something less dense, like a gas, will only absorb (or emit) certain types of light. A solid can also give off light at pretty much all wavelengths if it is heated up. For a strange reason physicists refer to a solid light source as a black body . Yes, that's right, an object that is giving off light because it is heated up is called a black body. This is in part due to the fact that such objects also absorb light, like how dark clothing is worn in cold weather to keep you warmer. There are a bunch of complicated formulas that define how "true" black bodies
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This note was uploaded on 12/15/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.