Infrared Radiation and Temperature

• Infrared radiation


  What you feel as heat
• Every object absorbs and emits infrared radiation
• Infrared radiation emission


  1. Infrared radiation is emitted from the surface of an object

  2. The hotter an object is, the more infrared radiation it radiates in a given time

  3. An object that's hotter than its surroundings emits more IR radiation than it absorbs as it cools down

  4. An object that's cooler than its surroundings absorbs more IR radiation than it emits as it warms up

  5. Objects at a constant temperature emit infrared radiation at the same rate that they are absorbing it
• Surfaces


  • Some colours and surfaces absorb and emit radiation better than others
  • A black surface is better at absorbing and emitting radiation than a white one
  • A matt surface is better at absorbing and emitting radiation than a shiny one
• Investigating absorption with the melting wax trick

  1. Set up equipment with two metal plates, one with a matt black side and one with a silver side, each with a ball bearing stuck on with wax

  2. The plates are placed the same distance from a Bunsen burner flame

  3. The ball bearing on the black plate will fall first as the black surface absorbs more infrared radiation, transferring more energy to the thermal energy store of the wax