ASTR 101 Lecture 22: Continuation on Light and Atoms

• School: Queen's University
• Department: Physics, Engineering Physics and Astronomy
• Course: ASTR 101
• Professor: David Alan Hanes

Document Summary

Lecture 22 - continuation on light and atoms. Stellar spectrum: absorption spectrum given off by the star. Not always in colour; long spectrum with lines; can detect what element it contains; but cannot detect how much of it is in the star. Earth"s atmosphere has affect on the spectrum (oxygen, etc) Maybe gas between earth and sun, affecting the spectrum. Dominant affect: thin atmosphere around outskirts of the star. Temp causes affect on the spectrum but generally, stars are composed of hydrogen and nitrogen. Light as particles: photoelectric effect (einstein won nobel prize for explaining it) Used in expose meter in cameras, automatic doors in elevators. Certain materials will eject electrons when light is shined on it. Red light doesn"t eject electrons, green light ejects some electrons (more when more intense), blue light ejects electrons at a high speed! (even using the dimmest blue light) The amount of energy it carries is key to ejecting electrons.