#### Spastik_Relativity

This is quite homework but i did think about it whilst at school and i wasnt sure where to post it.

In the entire electromagnetic spectrum our eyes can only view the visible wavelengths of photons.

My teacher said this and it lead me to think why this is so.
I've breifly looked on the internet and havent found anything in particular to help me out. So ive got two questions for anybody to answer.

Why can our eyes only see the visible wavelengths of the electromagnetic spectrum?

And, can other animals or organsims view the other spectrums?

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#### Galileo

Homework Helper
Our eyes can only detect light with wavelengths in the visible spectrum, otherwise it wouldn't be called visible light.

At the lower end (long wavelength) there is the infrared, which we cannot see, but the python can (I think).
At the other end (short wavelength) there is the ultra-violet which we cannot see, but the bee has an eye that can see it. Or it might be the other way around...

If you look at the intensity spectrum of the sun's radiation as a function of wavelength you'll see it's peaked around a wavelength interval which is exactly that interval wherein our eyes are sensitive. Apparantly our eyes have evolved in such a way as to pick this range of wavelengths, since it is probably most convenient for us humans.

#### Spastik_Relativity

thats interesting

so it is infact our eyes that make those certain wavelengths the 'visible' wavelngth and not the properties of the photons

#### HallsofIvy

Homework Helper
Spastik_Relativity said:
thats interesting

so it is infact our eyes that make those certain wavelengths the 'visible' wavelngth and not the properties of the photons
If you mean by this that our eyes cause photons to be a certain wavelength then no, a given photon has a certain energy and therefore a certain wavelength. The point that others are making is that our eyes only "process" certain wavelength photons- the others result in no impulse to the brain. It's a lot like the "photo-electric" effect- only certain wavelengths (certain energies in terms of photons) will trigger an optic nerve in the retina.

#### kevinalm

Galileo said:
At the lower end (long wavelength) there is the infrared, which we cannot see, but the python can (I think).
Pit vipers, for example the rattlesnake. The pits are cavities with a heat sensitive lining. Works like a pinhole camera of sorts. The resolution isn't very good but they do seem to be able to direct a strike at warm blooded prey. I don't think any of the constrictors have pits.

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#### Spastik_Relativity

If you mean by this that our eyes cause photons to be a certain wavelength then no, a given photon has a certain energy and therefore a certain wavelength. The point that others are making is that our eyes only "process" certain wavelength photons- the others result in no impulse to the brain.
sorry by my first statement i meant that its is that human eyes can only process the photons in the visible wavelength of the electromagnetic spectrum.

It's a lot like the "photo-electric" effect- only certain wavelengths (certain energies in terms of photons) will trigger an optic nerve in the retina.
thats an interesting point. Im not a biologist and frankly i have no idea about the structure of the eye but does the "make-up" of our eyes restricting the ability to view other wavelengths

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