radiation

• radiation - 3rd move of heat transfer. it involves heat from one object transferring in the form of waves and being absorbed by another object
• the sun gives off heat in all directions
• radiant energy can travel without the help of molecules of matter
• hot objects emit electromagnetic waves wherein no medium is required to propagate
• the energy of the electromagnetic radiation depends on the wavelength, which is evident in the color of the object
• a smaller wavelength has a higher frequency which corresponds with higher energy
• human skin - good absorber and emitter of infrared radiation
• emissivity - measure of how well an object radiates
• a perfect radiator has an emissivity value of 1
• a perfect reflector has a emissivity value of 0
• white shirt - poor absorber
• white objects reflects all radiation
• human skin has an emissivity values of o.97
• the high value of emissivity of our skin is why we can easily feel radiation
• earths temp - is a result of the balance of energy between the incoming radiation from the sun and the energy radiated from the earth
• this re-radiation back to earth that maintains the surface temperature of the earth
• carbon dioxide and water - absorb most of the infrared radiation emitted from the earth and then re-radiated back to the earth or into the outer space
• greenhouse effect - responsible for providing temp appropriate for life on earth