infrared radiation

• • infrared is emitted from the surface of an object
  • the hotter the object, the more infrared radiation is emitted
  • the hotter the object, the more emitted radiation is visible light
• • an object hotter than its surroundings emits more infrared radiation that it absorbs as it cools
  • an object colder than its surroundings absorbs more infrared radiation than it emits as it warms
• • objects at constant temperature emit infrared radiation at the same rate as it absorbs
• practical:

  1. place empty Leslie cube with 4 painted surfaces (matte black, matte white, shiny black, shiny silver) on heatproof mat
  2. fill cube with boiling water and replace lid
  3. leave for one minute so surfaces can heat up to temperature of water
  4. hold infrared detector 10cm away from each face and record infrared radiation emitted from each face