Lecture on Thermal Radiation

Key Concepts

• Types of Heat Transfer
  • Conduction
  • Convection
  • Radiation

Focus on Radiation

• All Objects Emit and Absorb Infrared Radiation

  • Even humans emit small amounts detectable by thermal imaging cameras
  • Cameras detect infrared and convert it to visible light

• Relationship Between Temperature and Radiation

  • Hotter objects emit more radiation
  • Hot objects can emit visible light

• Infrared Radiation

  • Type of electromagnetic radiation
  • Lower frequency than visible light
  • Involves waves, not particles

• Behavior in Space

  • Can pass through the vacuum of space
  • Explains why we feel the Sun's heat despite its distance

Surface Properties and Infrared Radiation

• Dark, Matte Surfaces

  • Good emitters and absorbers of infrared radiation
  • Example: Solar panels are black to absorb more heat

• Light, Shiny Surfaces

  • Poor absorbers and emitters of infrared radiation
  • Good reflectors of radiation
  • Example: Thermos with shiny inner coating to reflect radiation and keep contents warm

Applications

• Thermal Imaging Cameras
  • Detect emitted infrared radiation
• Solar Panels
  • Black to maximize heat absorption
• Thermos
  • Keeps contents warm by reflecting radiation