why infrared radiation heats but visible spectrum doesnt?

[netrat]

Description:-

We associate heat with infrared radiation. And temperature is only intermolecular/atomic motion.

infrared rays heatup a metallic rod and causes expansion.

infrared photon has lesser energy than visible photon.

 

case1: Take pure incident visible photon and shine it over a metallic rod for long time.

question: Will the rod heat up and expand?

 

case2: Now Cause fluctuation of visible photon over the metal.

question: Will it heat faster?

 

In any case does infrared photon heat metal faster than visible photon?

If yes. why?

[Mr Skeptic]

Photons of all types can heat just fine. The visible wavelength photons carry more energy per photon than do the infrared photons, so can heat more each. However, due to the distribution of light that gets emitted by hot objects, they emit comparatively brightly in infrared, and so the infrared portion carries a lot of the energy.

 

Other than that, different colors of light may be absorbed differently by different color compounds. Since only absorbed light will heat an object, its color also matters.

[netrat]

Photons of all types can heat just fine. The visible wavelength photons carry more energy per photon than do the infrared photons, so can heat more each. However, due to the distribution of light that gets emitted by hot objects, they emit comparatively brightly in infrared, and so the infrared portion carries a lot of the energy.

 

Other than that, different colors of light may be absorbed differently by different color compounds. Since only absorbed light will heat an object, its color also matters.

 

So that is to say that if i shine blue light over iron-oxide, it will heat up more than when i shine red light [keeping intensity same]?Because ironoxide being red, reflects back any red light and doesnt absorb it.

Edited December 7, 2010 by zacinfinite

[Mr Skeptic]

Right, and infrared is a color like any other. For example, you could say that infrared is the color of carbon dioxide. Although at that point it's usually talked about as an absorption spectrum, since we can't really see infrared.