Why can humans not see infrared radiation?

Answer 1

Based on evolution it has never been necessary for our existence so we would not have developed this. Others that benefit from it have, like the kestrel, and a species of shrimp for example can see into the ultraviolet spectrum.

Answer 2

We cannot see the other spectrum of electro-magnetic radiation because our eyes are not equipped with the proper sensors to "sense" the other forms of electromagnetic radiation.

Now only if we could see a fourth colour....

Humans use photopsin and rhodopsin proteins to see. These proteins are only sensitive to a certain band of photon energies.

Lower-energy photons don't have enough energy to trip those proteins into the alternate shape which triggers a cascade of signals eventually leading to sight.

Higher-energy photons are blocked by the lens, it is actually possible to see UV with the lens removed (the lens only accounts for 30% of the focusing power of the eye). Aphakic patients can see in UV, there is even a myth that they were used to spot German U-boats with UV search lights in WW2.

We are blind to photon energies outside those bands.

Fortunately for us, most of the light from our sun happens to be in this band of visible light. Some people would say this is not a coincidence. We evolved with the sun as our main source of light. So if the 'visible spectrum' of light is the dominant form of light emitted from the sun, then it makes sense that we would view in the 'visible spectrum'.

(Should I say something about the 1967 Nobel Price given to George Wald?)

Answer 3

The human eye has 2 types of photoreceptor cells. Rods, which are very sensitive to light (Which allow us to see in low light) and cones, which are less sensitive to light and give us vision when there is a lot of light. Cones have 3 sub-types: Red, green and blue. Color works by each subtype detecting light in their wavelength (650nm, 510nm and 475nm, respectively) and firing bipolar and amacrine cells to the retinal ganglion cells, via neurons, which then transmit data to various regions of the brain, again via neuron paths through other cells. Depending on how many times each was fired, the brain figures out color. The color we see is actually wavelengths of light. No retinal cells are known to exist in humans that are sensitive to wavelengths over 700nm (700nm being visible as a deep red), hence we cannot "see" infrared light. The same goes for ultraviolet light, which is 10nm and under. Rods are most sensitive at 498nm but do not have the color subtypes for the brain to figure out color, hence why everything looks black and white in the dark when your eyes acclimate.

Unnecessary further explanation of rods: Rods don't have color subtypes because in order for there to be any resolution in the dark at all multiple rods must be connected to a single neuron. This causes the brain to be unable to know which individual rod fired. If there were color subtypes, I would imagine vision would be very strange, with colors bleeding everywhere.

*infrared light: electromagnetic radiation with wavelengths longer than visible light but shorter than radio waves.

Higher Level Explanation: The shortest wavelength is violet and the longest wavelength is red. Waves that have a wavelength just a bit shorter than violet are considered ultraviolet. They are stronger than visible light and can't be seen. Waves that are just a bit longer than red are called infrared. Infrared waves are weaker than visible light and cannot be seen.

Simpler Explanation: The naked human eye can't see infrared light, because the naked human eye only has a limited spectrum of lights/colors that it can see. Infrared light isn't in the visible spectrum.

Yes it is true that the shortest wavelength is violet and the longest wavelength is red, and that the human eye can't see Infrared light because it only has a limited spectrum, but technology has giving us the power to see what we call " Infrared Light" ,in cameras, Ipods, Ipads, Apps from the computer ( if you have a webcam ) and other many ways you could. To know more about this you can Sign-Up to Fcat Explorer ( not for free, you must pay the program when you sign-up ,but you can sign-up for the free trial) than click on Middle School Voyage, and finally click on : Physical & Chemical. I hope this helped all of you guys to understand what Infrared light means and the cause why human eye can't see ifrared light.

Answer 4

Humans perceive colour using the cone cells on our retinas. These cone cells generate nerve impulses (through a rather complex and backwards mechanism) when they are stimulated by certain wavelengths of light. Unfortunately humans do not have cone cells that can respond to stimulation by infrared light and therefore we cannot directly perceive infrared ligh as vision.

Answer 5

The human eye can only see a narrow spectrum of the electromagnetic spectrum because of the way photoreceptive cells in the eye work:

They consist of a pigment molecule that responds to a small band of frequencies. There are three types of pigment in human eyes: Red, blue, and green.

These pigments produce an electrical impulse when they are struck by EM Radiation (EMR) of their band, and your brain translates these impulses into vision.

The pigment in the cells doesn't produce an electrical impulse when it absorbs EMR of any frequency other than the small range to which it is tuned, so X-Rays are invisible to humans

If there was, for instance, an Ultra Violet pigment in some of the cells in human eyes, they would be able to perceive UV radiation the same way they do visible light. UV would effectively be part of the visible spectrum.

Answer 6

We have given the name "visible light" to the entire range of frequency/wavelength that

we can see. In that way, we have attached the label "visible light" to all electromagnetic

waves to which human eyes are capable of responding.

The label is exact ... everything we can see gets the label, and nothing we can't see gets it.

And that is why we can only see visible light . . . because if we could see any other wavelength,

then we would immediately start to call that one "visible light" too.

Answer 7

because they are present at the invisible portion of the electromagnetic spectrum

Answer 8

infared light cannot be detected by human eyes because the wavelength of them are too long for our limited visible spectrum. hope that helped ,

Answer 9

Actually we can see red light, unless you are colour blind to the colour red.

Humans cannot see infrared light