Infrared practical

• Investigating how much infrared radiation is absorbed or radiated by different surfaces

  1. Fill Lesley's cube with hot water

  2. Point infrared detector at each surface

  3. Record amount of infrared emitted

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


  • Has 4 different surfaces: shiny metallic, white, shiny black, matte black
• Matte black surface


  Emits the most infrared radiation
• Shiny metallic surface


  Emits the least infrared radiation
• Infrared detector


  More sensitive than a thermometer, can detect smaller changes
• Measuring absorbance of infrared by different surfaces

  1. Use infrared heater and metal plates

  2. One plate painted shiny metallic, other painted matte black

  3. Attach drawing pins to plates with Vaseline

  4. Switch on heater and time how long it takes for pins to fall off
• Matte black plate


  Drawing pin falls off first, absorbs more infrared
• Shiny metallic surface


  Tends to reflect infrared instead of absorbing it
• Matte black surfaces are much better at emitting and absorbing infrared than shiny metallic surfaces