infrared required practical

• Glowing coals are emitting visible light
• Hot surfaces also emit infrared radiation
• The human eye cannot see infrared
• Lesley's cube


  A device used to investigate how much infrared is emitted or absorbed by different surfaces
• Surfaces in a Lesley's cube

  • Shiny metallic surface
  • White surface
  • Shiny black surface
  • Matte black surface
• Using a Lesley's cube to measure infrared emission

  1. Fill with hot water

  2. Point infrared detector at each surface

  3. Record amount of infrared emitted

  4. Keep same distance between cube and detector
• Findings from Lesley's cube experiment

  • Matte black surface emits the most infrared
  • Shiny black surface emits less than matte black
  • White surface emits less than shiny black
  • Shiny metallic surface emits the least infrared
• Thermometer


  Can be used instead of infrared detector, but has lower resolution (smaller changes can be detected)
• Measuring infrared absorbance


  1. Use infrared heater

  2. Two metal plates, one shiny metallic, one matte black

  3. Attach pins to plates with Vaseline

  4. Time how long it takes for pins to fall off as plates heat up
• Findings from infrared absorbance experiment

  • Matte black plate absorbs more infrared, pin falls off first
  • Shiny metallic plate absorbs less infrared, pin takes longer to fall off
• Matte black surfaces are much better at emitting and absorbing infrared than shiny metallic surfaces
• Infrared tends to be reflected from shiny metallic surfaces