emissivity, absorptivity,black body
2006-11-08 13:53:54 · 4 answers · asked by DEV 1 in Science & Mathematics ➔ Physics
It is one of the ways heat is transported. The other two are conduction and convection.
2006-11-08 14:53:11 · answer #1 · answered by Dr. J. 6 · 0⤊ 0⤋
The emissivity of a material ranges from 0 to 1 and is the probability that radiation will be absorbed or emitted. A shiny material has low emisivity and a black body has an emissivity of 1 by definition. A black body is a perfect absorber. The total radiation from a thermal source is given by E=esT^4, where e is the emissivity, s is the Stefan-Boltzman constant and T is the temperature. The Planck distribution (see ref, I don't want to type it) gives the frequency dependence of the radiation. The absorptivity is a measure of the probability that radiation of a particular frequency will be absorbed by a material. Heat radiation is an inprecise term that generally refers to near infrared radiation between 700 and 3000 nm. This near infrared radiation is effective at heating because many common materials absorb in the near infrared. The term is inprecise because no heating will occur for materials that are transparent in the near infrared.
2006-11-08 18:42:45 · answer #2 · answered by d/dx+d/dy+d/dz 6 · 0⤊ 0⤋
Yes, it is simply the 'emission' of heat that you feel when you stand in front of a fire or a heater or a 'radiator' to get warm.
You absorb it.
What black body are you talking about ... a black hole (?) has nothing to do with your question.
Good luck,
J.
2006-11-08 14:20:00 · answer #3 · answered by Jonnie 4 · 1⤊ 0⤋
Infrared part ot the electromagnetic spectrum.
2006-11-08 13:58:44 · answer #4 · answered by hrwwtp 4 · 0⤊ 0⤋