[katieHaylor (OP)]

Damon asks:

Why does infrared light make us warm, considering red light has a longer wavelength and lower frequency thus lower energy?

What do you think?

[PmbPhy]

Why does infrared light make us warm

I'm not certain but I think it has to do with the way the material we're made of absorbs radiation. Hit us with red and the atoms get excited, some going into thermal energy. Hit us with infrared and most of the energy goes into the kinetic energy of motion of our atoms. How hot we get also depends on the number of photons we're hit by per second.

Try searching Google on this. You may find a better answer.

[evan_au]

red light has a longer wavelength and lower frequency thus lower energy?

Red photons have a longer wavelength and lower energy than blue photons, and blue photons have less energy than ultraviolet photons.

If you were hit by the same number of watts of ultraviolet light as there is red light from the Sun, you would be warmed by a similar amount, but you would also suffer severe sunburn, as ultraviolet photons can damage your DNA, when the same power level of red photons won't damage DNA.

But the Sun puts out less UV than red light, due to its black body temperature of around 5000K. And a lot more infra-red than visible light.
See: https://en.wikipedia.org/wiki/Black-body_radiation

However, Earth's atmosphere blocks most UV light, while letting through most infra-red.
See: https://en.wikipedia.org/wiki/Atmosphere_of_Earth#/media/File:Atmospheric_electromagnetic_opacity.svg

So although UV photons individually have more energy than IR photons, the IR photons are far more numerous, and carry far more power to be absorbed by your body.

So IR radiation from the Sun does make us feel warmer than blue light.

The ratio is even more extreme for a gas or electric heater, since the black body temperature is much lower, and almost all of the energy is emitted as IR.

[Colin2B]

The big difference between IR & UV is how they are absorbed. Long-wavelength IR is not scattered but is absorbed by water in the soft tissues and this causes the sensation of heat when the water molecules are excited. Ultraviolet radiation, especially with short wavelengths eg UV-B, is absorbed by bulk tissue containing proteins, lipids and DNA which are easily damaged. Most of the UV-B radiation is therefore absorbed in the outer superficial layer, epidermis, and this is why we tend to get sunburn.

[MartyParty]

So, the main source of radiation emmitedd by the sun is Black Body Radiation (BBR).
Black body radiation is like, when we heat an object to a non-zero temperature it radiates EM waves, and if it was completely black we could calculate the energy of the EM waves emitted by the BBR. EM waves are almost perfectly absorbed by plasma(the sun is like ahuge plasma ball), which makes it practically "black" in a regard to the EM waves, so when we did the experiment with the sun we found out it emits all kinds of radiation, most of which is visible light for our eyes, then IR(infra-red) and UV(Ultraviolet) light, with relatively low amount of radio and gamma rays emitted. Now those IR and UV light-rays travel from the sun towards the Earth and react with the upper atmosphere and the magnetic field. Most of the radiation is absorbed by the atmosphere, while the rest is relfected, hence the albedo effect of the planet(the albedo is a way of measuring how much light a certain planet reflects or absorbs it can take values between 0 and 1, the Earth's albedo is about 0.367). Huge portion of those UV light-rays are reflected back by the atmosphere, some eventually make it throught the atmosphere and hit the ground(You get sunburn because of the UV rays, which is actually bad because they can damage your cells and DNA). While infrared on the EM spectrum is lower energy than the UV, it means it has a longer wavelength than the UV radiation, so it penetrates through the atmosphere easier(correct me if i'm wrong), and some of it is relfected back either by the atmosphere or the ground. Tho, you might think of infrared sensors, like you might've seen in some movies, where the sniper hides in a bush or a high place, during the night and looks at his target with the IR sensor, and sees his victim in red/yellow colors and when he shoots it becomes blue. Well this is infrared light, humans emit IR light, but we cannot see it because our eyes aren't as sensitive as some other animals' eyes. But let's see what Infrared means, well as far as  i know infra means "below" and red is like the color red so IR means below red, thus the color below red, so you'd be getting some minimal amount of heat but, i think it'd be insfficient for our bodies to feel it.