Required Practical 10:Infared

• What is the purpose of the practical described in the video?

  To investigate how much infrared radiation is absorbed or radiated by different surfaces.
• What equipment is used to measure infrared radiation in the practical?

  • Lesley's cube
  • Infrared detector
  • Thermometer (with the bulb painted black)
• What surfaces are compared in the Lesley's cube experiment?

  Shiny metallic, white, shiny black, and matte black surfaces.
• Why is it important to keep the same distance between the Lesley's cube and the infrared detector?

  To make the measurements repeatable.
• Which surface emits the most infrared radiation according to the experiment?

  Matte black surface.
• Which surface emits the least infrared radiation?

  Shiny metallic surface.
• How can infrared absorption be measured using metal plates?

  • Use an infrared heater.
  • Attach drawn pins with Vaseline to two metal plates (one shiny metallic, one matte black).
  • Record the time it takes for the Vaseline to melt and the pins to fall off.
• Which plate does the drawn pin fall off first, and why?

  The pin falls off the matte black plate first because it absorbs more infrared.
• What is the relationship between surface color and infrared absorption/emission?

  • Matte black surfaces emit and absorb more infrared.
  • Shiny metallic surfaces reflect infrared and emit/absorb less.