Why can't we see light outside the visible spectrum? Can other animals see outside these wavelengths?

Question

Why does our visual range stop outside the 400-700nm (approx) wavelength range of light? Are there people or animals who have a greater range than this? I have heard that some insects (bees to be precise) can see in the ultra violet and infa-red range.

Is it biologically impossible to see beyond this or is it just the result of evolution cutting out any wavelengths that would not be of any use to us? Can we see the full spectrum of light but our brains filter out anything that isn't in this range? Any web references would be very useful.

FOA Morey000 - I believe that sunlight has more wavelengths than just the visible spectrum. Infact the range of wavelengths in sunlight is huge an way beyond the human visible range so I'm afraid your theory doesn't hold water. Golley.

Answer 1

The term "visible spectrum" is completely subjective! If we could see light of wavelengths beyond the visible spectrum, those wavelengths would also be part of our 'visibility spectrum'. Colourblind people don't see certain wavelengths of light WITHIN the 'visible spectrum'.

This is because our retinas contain photoreceptors ('rods' and 'cones') that respond only to the 'visible' spectrum. You can think of light as like a radio signal (in fact, since light and radio waves are both part of the electromagnetic spectrum, they are the same!)—our eyes are only 'tuned' to a particular range of light wavelengths, just as a radio can only pick up a certain range of radio wavelengths. Other signals might be present, but can't be detected with that equipment.

Pollinating insects see a 'visible spectrum' that goes some way into (what we call) the ultraviolet range, allowing them to zero in on flowers (coloured pigments quite often fluoresce in the UV range, making the flowers easier to home in on). We don't, because being able to see UV doesn't confer any evolutionary advantage on primates (including humans), as we don't feed exclusively on flower nectar.

Evolution tends to produce abilities which increase an individual's probability of survival and reproduction. We don't need this ability, therefore we haven't developed it.

In theory, if you could implant the gene for the insect UV photoreceptor into the human genome, and get it to activate properly (i.e. only in retina cells), then humans would also be able to see UV. But there would be no reason to do so (and that kind of thing is still illegal anyway!)

Answer 2

Most animals see a similar spectrum as human beings, some with some small extensions into infrared or ultraviolet.

This has a simple reason: That's a window in the opacity of water. You can't see infrared or ultraviolet light though water, nor radio or radar.

The nature developed the concept of eyes under water, so it was useful to chose that range of frequencies. Even on land it's useful to use that, as air contains a lot of water. During the evolution some animals (for example bees) extended that range , because it's important for them to identify flowers, and they have a characteristic appearance in the UV range.

Another reason is that the atmosphere is not very transparent for UV light, so in that range it is, compared to the visible spectrum, quite dark on earth.

Answer 3

it is not biologically impossible to 'see' outside of this range. Our spectral visibility is so because of evolution. It just so happens that in order to survive, this is the most useful range of frequencies to see. Had there been no light (or poor light) in this range (and assuming that living conditions were still fundamentally there) then we might well have developed vision in the infrared or ultraviolet ranges. Evolution did not cut out other frequencies, we simply didnt develop that capability in other ranges because it was of little or no use next to the spectrum we do use.

There have been rats bred to glow in the dark, and annecdotal evidence of some people receiving radio reception through their fillings so it is not inconceivable that we could alter our own genetic code to see in a different range. This could have military possibilities and I wouldnt at all be surprised if somebody were working on it already.

Answer 4

It's not biologically impossible, it's just that we animals have evolved using the spectrum given to us. Our eyes just so happen to be most sensitive at the frequency of the sun. Golly? A coincidence.

but yes- some animals, like bees and butterflies, skew to the UV. Apparently it helps them identify flowers.

Answer 5

This structure of a prism is such that it disperses white light into component colors. Rain drops disperse light by total internal reflection (TIR) thereby producing rainbow. Our eye lens is not of the shape which can disperse light. Eye lens forms a sharp, real and inverted image on the retina, the retina communicates this image to the brain via the optic nerve. Hope that helps :)

Answer 6

It's not that our brain filters out the rest of the spectrum but that our eyes cannot sense it.

Think of:
light as sound
wavalenght as frequency and
your eyes are your ears

This should help you imagine that your eyes (ears) are not tuned to the right frequency (wavelenght) and this is why we can't see UV and IR light.

This should make it easier to understand why we can't see all white light.

As for evolution........well I could not tell you about that- it's not my thing

Answer 7

I have heard that some canines can see infrared, but my dog, who chases a flashlight spot, won't chase the spot made by my remote control. Most video cameras will pick up IR. Try pointing your remote control at your video camera.

Answer 8

Yes very few do. But it is nor seeing. Like radar and ultrosonic etc

Answer 9

not sure, dogs only see in black and white i heard though

Answer 10

Its something to do with God, and him doing stuff during seven days, and then going skiing or something.