ASTR 151 Lecture Notes - Lecture 11: Cosmic Microwave Background, Black Body, Electromagnetic Spectrum
Document Summary
Visible portion of the electromagnetic spectrum is very small. The scale is logarithmic which means that each tick mark is 10 times the previous. Shorter wavelength= purple (gamma) (from longest to shortest) radio waves, microwaves, infrared, visible, ultraviolet, x- rays, gamma rays. Spectral windows- light from electromagnetic spectrum that reaches the ground. Temperature- a measure of the average microscopic motion. All thermal motions theoretically cease at absolute zero. Black body- an idealized body that absorbs, and reradiates, all wavelengths of light perfectly. A blackbody spectrum tells how much of each wavelength of light a body with a temperature is giving off. Blackbody characterizes the electromagnetic radiation or light. As a function of temperature, every temperature has a unique blackbody spectrum: ex. 100 units of energy per second hitting the black body from a uv laser. Total energy out all 100 units of energy but now spread out over a lot of wavelengths.
