During yesterday’s blog post about why our bodies can feel infrared light but not UV rays there was a portion of the discussion talking about whether LED light photons give off heat. I thought that it would be interesting to write about how light particles give off heat or are the photons themselves what give off the heat?
Question: Does infrared heat emit infrared photons or are infrared photons what give things heat?
Answer: I guess another way to describe this questions is by saying do you mean why does your body heat up when the sun shines? Or, why does your body heat up in an infrared sauna?
The sun emits photons, and photons carry all kinds of energy. When these energized photons come in contact with your skin, they’re either absorbed, transmitted or reflected. Which of these three processes happens will depend on the wavelength of the light particle (or photon), the angle of entry and the material the photon hits.
If the particle/photon is absorbed by your body, its energy has to go somewhere to be conserved. Therefore, the energy of the photon may be converted to heat inside of your body. Infrared light is a longer wavelength which is at the perfect wavelength to activate, energize and charge (through molecular motion) your body’s molecules of your cells which then raise their temperature on the whole. This is why an infrared sauna raises your core body temperature–all of your cells are absorbing the infrared energy.
Photons of any part of the light spectrum can heat up an object; however most of the objects on earth emit black body radiation (or put out infrared light themselves) in the infrared spectrum. This is the reason why we can see warm bodies with infrared cameras or why we can use infrared night vision–things on Earth emit infrared light as heat!
Infrared tea anyone?