infrared

• What is the main objective of the practical described in the video?

  To investigate how much infrared radiation is absorbed or radiated by different surfaces
• Why is it important to learn the details shown in the video?

  Because it is a required practical
• What do glowing coals emit besides visible light?

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

  Because infrared radiation is outside the visible spectrum
• What is a Lesley's cube used for?

  To see how much infrared is emitted from different surfaces
• What surfaces are present on a Lesley's cube?

  Shiny metallic, white, shiny black, and matte black surfaces
• What is the first step in the practical using a Lesley's cube?

  Fill the Lesley's cube with hot water
• 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?

  Matte black surface
• What is the order of infrared emission from the surfaces tested?

  Matte black, shiny black, white, shiny metallic
• What can be used if an infrared detector is not available?

  A thermometer with the bulb painted black
• What is the resolution of a thermometer compared to an infrared detector?

  The resolution of the thermometer is less than that of the infrared detector
• Why might a thermometer not detect large differences between surfaces?

  Because its resolution is lower than that of an infrared detector
• What equipment is used to measure the absorbance of infrared by different surfaces?

  An infrared heater and two metal plates
• What is painted on one plate in the absorbance experiment?

  Shiny metallic paint
• What is painted on the other plate in the absorbance experiment?

  Matte black paint
• What happens to the temperature of the metal plates when the infrared heater is switched on?

  The temperature of the metal plates increases as they absorb infrared
• What is recorded in the absorbance experiment?

  The time it takes for the Vaseline to melt and the drawn pins to fall off
• Which plate does the drawn pin fall off first?

  The matte black plate
• Why do matte black surfaces absorb more infrared than shiny metallic surfaces?

  Because matte black surfaces are better at absorbing infrared
• What happens to infrared radiation when it encounters shiny metallic surfaces?

  Infrared tends to be reflected from shiny metallic surfaces
• What are the key surfaces tested in the infrared radiation practical?

  • Shiny metallic surface
  • White surface
  • Shiny black surface
  • Matte black surface
• What are the steps to investigate infrared radiation absorption and emission?

  1. Use a Lesley's cube filled with hot water.
  2. Measure infrared emission with an infrared detector.
  3. Use an infrared heater and metal plates to measure absorption.
  4. Record the time for Vaseline to melt and pins to fall off.
• What are the differences in infrared emission and absorption between matte black and shiny metallic surfaces?

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