This color of light can be produced either by using helium-cadmium lasers, or frequency doubling the ground-state transition for neodymium-doped YAG, in which case you have a quasi-three-level gain medium, instead of a four-level.
This color of light can be produced either by using helium-cadmium lasers, or frequency doubling the ground-state transition for neodymium-doped YAG, in which case you have a quasi-three-level gain medium, instead of a four-level. In a quasar's spectral energy distribution, thermal emission from gas in an accretion disk creates a big bump named for this color. LEDs of this color use indium gallium nitride or gallium nitride substrates. Horizontal-branch stars, common in globular clusters, are often alternately named for a "loop" of this color. Stars of this color typically have a spectral type of O, B, or A, and are plotted on the left side of an HR diagram, in contrast to red stars on the right. For 10 points, identify this color, which Rayleigh scattering imparts to the Earth's atmosphere.
This color of light can be produced either by using helium-cadmium lasers, or frequency doubling the ground-state transition for neodymium-doped YAG, in which case you have a quasi-three-level gain medium, instead of a four-level.
blue [or violet; or obvious equivalents]