Infared

• Why can't the human eye see infrared radiation?

  Infrared radiation is outside the visible spectrum
• What is a Lesley's cube used for in this practical?

  To measure infrared emission from surfaces
• What surfaces are present on a Lesley's cube?

  Shiny metallic, white, shiny black, matte black
• How do you ensure repeatable measurements in the experiment?

  Keep the same distance between the cube and detector
• Which surface emits the most infrared radiation according to the experiment?

  Matte black surface
• What is the resolution of a thermometer compared to an infrared detector?

  The thermometer has less resolution than the detector
• What equipment is used to measure the absorbance of infrared by different surfaces?

  Infrared heater and metal plates
• What happens to the temperature of the metal plates when the infrared heater is switched on?

  The temperature increases as they absorb infrared
• What is the effect of shiny metallic surfaces on infrared radiation?

  They tend to reflect infrared radiation
• What are the steps to investigate infrared radiation absorption using a Lesley's cube?

  1. Fill the Lesley's cube with hot water.
  2. Point an infrared detector at each surface.
  3. Record the amount of infrared emitted.
  4. Ensure consistent distance for repeatability.
• What are the differences between matte black and shiny metallic surfaces in terms of infrared?

  • Matte black surfaces:
  • Emit more infrared
  • Absorb more infrared
  • Shiny metallic surfaces:
  • Emit less infrared
  • Reflect infrared radiation