In hot countries, people paint their houses white to reduce absorption of heat energy from the Sun.

   Higher tier only:

     Thermal radiation is the transfer of heat energy by waves. 

     These waves are called infrared waves, they are electromagnetic waves.

  Thermal radiation travels through vacuum.

  Objects give out (emit) and absorb heat energy all the time.

  No particles move in thermal radiation.

  The hotter the object the more infrared it gives out.

Sun's heat travels through vacuum

  Dull black surfaces are better absorbers and emitters of heat than bright colour surfaces.

  Shiny surfaces are very good reflectors of thermal radiation.