CHEM 6A Lecture Notes - Lecture 4: Black-Body Radiation, Radiant Energy, Stationary Point

• School: UCSD
• Department: Chemistry and Biochemistry
• Course: CHEM 6A
• Professor: Thomas Bussey

Document Summary

Spectroscopy is the analysis of the light emitted or absorbed by substances. Wavelengths of visible light go from 400 nm to 750 nm: purple to red, 7. 5x10^14 hz to 4. 0x10^14 hz. Gamma is shortest, then comes x-ray, uv, visible, infrared, microwave, radio. The wave model of light cannot explain several phenomena: blackbody radiation, photoelectric effect. When objects are heated, they glow different colors with different intensities. Planck made the assumption that light could only have certain energy values in multiples of. A packet of light energy is a quantum. Each packet has energy h : e = h , h = planck"s constant, e = nh , n = number of photons. When light strikes the surface of a metal, electrons are ejected/emitted, creating a current if: the light had at least a certain frequency. Intense light at low frequencies does not cause electrons to be ejected.