XI Electromagnetic waves

1. wavelength and frequency
2. variations
3. emission – everything emits, depends on temperature, composition

1. selectivity wavelength dependence
2. transmission
   1. transparency
   2. absorbed and re-emitted
   3. affects speed of transmission
   4. controls color of transparent objects – absorbs all colors except the few transmitted soit appears the color of the transmitted few
3. absorption
   1. opacity
   2. energy excites the molecules, causing collisions and conversion of energy to heat
   3. black absorbs all and gains most heat
4. reflection
   1. white objects reflect all wavelengths
   2. gives color
   3. only reflect certain wavelengths
   4. if those wavelengths not available – not that color
5. scattering
   1. energy absorbed and re-emitted in all directions
   2. size of particle affects which wavelengths are scattered

1. blue sky .
2. red sunsets (subtraction of short wavelengths)
3. clouds