RADIATION

THERMAL ENERGY- RADIATION

radiation is the emission of infrared waves from the surface of all bodies-without the aid of a medium

• radiation does not require a medium


• therfore,can take place in a vacuum
  
• e.g heat from the sun reaches earth by radiation
  

RADIATION

• absorber : substance that takes in heat in the form of radiation (temp rises)


• radiator/emitter: substance that gives off heat in the of radiation (temps falls)


• reflector: substance that cannot absorb radiation (gd reflector=poor absorber,poor reflector=gd absorber)
  

the factors that affect the rate of heat transfer by radiation

1.colour and texture of the surface

• black,dull and rough surfaces are better absorbers of heat than shiny,white and smooth surfaces


• black,dull and rough surfaces are better radiators of heat than shiny,white and smooth surfaces


• black,dull and rough surfaces are poor reflectors or heat than shiny,white smooth surfaces

2. surface temperature

• the higher the temperature of the surface of an object when compared to the surrounding temperature,the higher the rate of infrared radiation from the object to the surrounding
  

3.surface area

-comparing between objects of the same mass and material,but with different surface area

• the object with the larger surface area will absorb heat better than the other


• the object with the larger surface area will also emit heat at a faster rate than the other