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A science question about the color spectrum

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gailryder17
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27 Apr 2011, 11:46 am

I know that we see color due to the electromagnetic waves our eyes detect. For example, we see that an apple is red because the waves of other wavelengths (on the color spectrum, as far as I'm concerned) are absorbed and the "red" wave is reflected and our eyes pick up that wave.

Black is when ALL of the wavelengths (that I'm concerned with) are absorbed, therefore our eyes pick up no wavelength. White is when ALL of the wavelengths are reflected, so all we see is white.

If so, then why do we see gray? Do we see parts of a wavelength, if that's possible. Do our eyes struggle to pick up all of a wavelength?

Also, why are humans only sensitive to the waves of the color spectrum (as far as eyesight goes. I know that our skin is sensitive to ultraviolet rays. Are humans sensitive to Infrared as well?)? What inhibits humans from seeing other waves (oooohhhh! maybe one day we can see in the dark!! !)



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27 Apr 2011, 12:00 pm

gailryder17 wrote:
I know that we see color due to the electromagnetic waves our eyes detect. For example, we see that an apple is red because the waves of other wavelengths (on the color spectrum, as far as I'm concerned) are absorbed and the "red" wave is reflected and our eyes pick up that wave.

Black is when ALL of the wavelengths (that I'm concerned with) are absorbed, therefore our eyes pick up no wavelength. White is when ALL of the wavelengths are reflected, so all we see is white.

If so, then why do we see gray? Do we see parts of a wavelength, if that's possible. Do our eyes struggle to pick up all of a wavelength?

Also, why are humans only sensitive to the waves of the color spectrum (as far as eyesight goes. I know that our skin is sensitive to ultraviolet rays. Are humans sensitive to Infrared as well?)? What inhibits humans from seeing other waves (oooohhhh! maybe one day we can see in the dark!! !)


We can pick up IR with the nerves in our skin. Of course it is not focused.

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27 Apr 2011, 12:10 pm

gailryder17 wrote:
I know that we see color due to the electromagnetic waves our eyes detect. For example, we see that an apple is red because the waves of other wavelengths (on the color spectrum, as far as I'm concerned) are absorbed and the "red" wave is reflected and our eyes pick up that wave.

Black is when ALL of the wavelengths (that I'm concerned with) are absorbed, therefore our eyes pick up no wavelength. White is when ALL of the wavelengths are reflected, so all we see is white.

If so, then why do we see gray? Do we see parts of a wavelength, if that's possible. Do our eyes struggle to pick up all of a wavelength?

Also, why are humans only sensitive to the waves of the color spectrum (as far as eyesight goes. I know that our skin is sensitive to ultraviolet rays. Are humans sensitive to Infrared as well?)? What inhibits humans from seeing other waves (oooohhhh! maybe one day we can see in the dark!! !)

Our eyes have adapted to be able to detect the visible spectrum wavelengths of light and grey is a partial absorption of all wavelengths of light


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gailryder17
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27 Apr 2011, 12:28 pm

Now, what determines which electromagnetic waves are absorbed and which are reflected?



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27 Apr 2011, 12:37 pm

Here may be a good start to explain it-may be too scietific but it hopefully can explain it better than I will ever be able to.
http://en.wikipedia.org/wiki/Reflectivity


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27 Apr 2011, 2:18 pm

gailryder17 wrote:
Now, what determines which electromagnetic waves are absorbed and which are reflected?


The receptors in our eyes. We have what is (very roughly) a biological version of the sensor array in a digital camera. The sensors - in the camera and in our eyes - only register the wavelengths they are suited to detect.

That analogy comparing our retinas to the sensor array in a digital camera is not perfect - no analogy ever is. But it does give you a useful way to comprehend what is happening, and why, as long as you're not trying to study biology in any depth.


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27 Apr 2011, 2:37 pm

gailryder17 wrote:
Now, what determines which electromagnetic waves are absorbed and which are reflected?


It's due to the energy states of the electron in the molecules of the surface. When they absorb the light, they're energy state is raised to a certain level, then when they go back to the "ground state", they release a certain wavelength of light. Different atoms and molecules will release different colors due to the different energy states between which their valence electrons move when absorbing and desorbing light.



ryan93
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27 Apr 2011, 4:18 pm

You can see UV, if you fancy removing your cornea. Fancy seeing a new colour?


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WillMcC
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27 Apr 2011, 5:37 pm

Most digital cameras can actually pick up infrared (try pointing a standard remote control at the lens and pressing buttons), and some can be modified by adding/removing filters to pick up just infrared for use in night vision, heat sensing etc.

Sensing gray is just a lower intensity of white. A computer or TV display uses three channels (red, green, blue) to display color. White is achieved by displaying each channel at a maximum value, and gray is displayed by equal values at a lower intensity.
A lot of it is relative anyway - a blank projector screen is white, but project an image onto it and the "black" is still white.
See also http://commons.wikimedia.org/wiki/File: ... lusion.PNG


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theWanderer
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27 Apr 2011, 7:02 pm

WillMcC wrote:
Most digital cameras can actually pick up infrared (try pointing a standard remote control at the lens and pressing buttons), and some can be modified by adding/removing filters to pick up just infrared for use in night vision, heat sensing etc.


But they don't normally "see" infrared in the images they produce (that is, a person's image is not different because they are hot from running, for example). And, as I pointed out, the analogy is not perfect. It was meant as a simple comparison to give a rough idea of why our eyes work the way they do.


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naturalplastic
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29 Apr 2011, 6:24 pm

Cats, and bees can see into the ulraviolet spectrum.

Some flowers that look flat white to humans actually have striking visual patterns which are revealed when photographed with UV film (that translates the UV to visible light).

Patterns meant for bees to see. .



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29 Apr 2011, 6:45 pm

naturalplastic wrote:
Cats, and bees can see into the ulraviolet spectrum.
As can birds. The additional feather patterning visible under UV is used to attract a mate.
http://www.hunterian.gla.ac.uk/whatson/ ... hp?item=12


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Dave02
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05 May 2011, 7:37 am

The human eye actually has a small response to IR. So if you block out all the visible light, you can actually see in IR.

ht tp: //amasci . com /amateur/irgoggl.html (had to break the link to make the forum software allow this post)

This guy details some filtering goggles he made that block all visible light but are transparent to IR. Pretty nifty stuff, but don't try to make UV goggles, it would be harmful to your eyes.



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10 May 2011, 7:02 pm

W usually have trichromatic(color) vision except for in low light where they become slightly tetrachromatic so that the range of wavelengths visible to us changes slightly. It isn't very noticible however.