required practical 10

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

  1. Observe glowing coals emitting visible light

  2. Understand that hot surfaces emit infrared radiation

  3. Use a Leslie's cube with 4 different surfaces (shiny metallic, white, shiny black, matte black)

  4. Fill Leslie's cube with hot water

  5. Point infrared detector at each surface and record infrared emission

  6. Ensure same distance between Leslie's cube and detector for repeatability

  7. Observe that matte black surface emits most infrared, followed by shiny black, white, and shiny metallic emits least

  8. Use a thermometer with black bulb if no infrared detector available, but less resolution

  9. Use infrared heater with two metal plates (one shiny metallic, one matte black)

  10. Attach pins to plates with Vaseline

  11. Switch on heater and time how long it takes for pins to fall off due to Vaseline melting

  12. Observe that pin falls off matte black plate first, as matte black absorbs more infrared than shiny metallic
• Infrared radiation


  • Hot surfaces emit infrared radiation
  • Infrared radiation cannot be seen by the human eye
• Leslie's cube


  • Has 4 different surfaces: shiny metallic, white, shiny black, matte black
  • Used to investigate infrared emission from different surfaces
• Infrared detector


  • Measures amount of infrared radiation emitted from surfaces
  • Provides more resolution than a thermometer
• Thermometer with black bulb


  • Can be used to measure infrared absorption if no infrared detector available, but has less resolution
• Infrared heater


  • Used to heat metal plates and investigate infrared absorption
• Matte black surfaces are much better at emitting and absorbing infrared than shiny metallic surfaces
• Infrared tends to be reflected from shiny metallic surfaces
• This is a required practical, so the details shown need to be learned
• There will be plenty of questions on this required practical in the revision workbook