Infrared

• What does every object absorb/emit?

  Infrared radiation
• The hotter the objects...

  the more IR it radiates
• If the object is hotter than the surroundings...

  emits more IR radiation than absorbs
• Objects at a constant temperature..

  absorb and emit IR at the same rate
• What is a perfect black body?

  An object that absorbs all incoming radiation and emits radiation at every wavelength. No radiation is reflected or transmitted.
• Earth's radiation: