black body radiation

• Blackbody radiation


  All objects, no matter what temperature, emit and absorb infrared radiation. Hotter objects emit more infrared radiation than cooler objects.
• Temperature of an object

  Depends on the balance between radiation absorbed and radiation emitted
• Blackbody


  • Absorbs all radiation incident on it, no radiation is reflected or transmitted
• Warmer object than surroundings

  Emits more radiation than it absorbs, causing its temperature to decrease
• Cooler object than surroundings

  Absorbs more radiation than it emits, causing its temperature to increase
• Constant temperature object


  Absorbing radiation at the same rate as it's emitting radiation
• How radiation affects Earth's temperature

  1. Sun emits short wavelength radiation (visible, UV)

  2. Some radiation is reflected by clouds

  3. Remaining radiation is absorbed by Earth's surface, increasing its temperature

  4. Earth emits infrared radiation back into space

  5. Greenhouse gases trap some of the infrared radiation, preventing it from radiating into space
• Human activity is increasing greenhouse gas levels
• Cloudy nights tend to be warmer than clear nights