# Seeing sunlight

Does anyone have an understanding of how sunlight works?
Tell me if I am wrong.
The sunlight travels in waves.
The length of the waves is how the eye sees color, the rainbow effect.
Everything in the universe vibrates at different wave lengths. Like heat has wave lengths is the reason ultraviolet light goggles work. (Wavelength is inversely proportional to the wave frequency) off the web.
Sunlight contains the spectrum of visible light.
So, a ray of sunlight hits a leaf on the tree. Sunlight hits that leaf and the light that is the same wave of the leaf is absorbed into the leaf.
Sunlight that is of a different wave length is reflected away.
Question; is the leaf really red in color and what we are looking at is the color the leaf is not? The waves that cannot penetrate and are reflected away and that is what enters the eye.
So, if that is the case then if we change the light source then the color of objects should change, for example using a black light or colored lights. It seems to work.
So are tree leafs really red and we are seeing the colors things are not?

Rather than trying to answer your questions, I’ll give a short summary of light.
All matter radiates a spectrum of energy with it’s mode of frequency dependent on the temperature of the item. At low temperatures the amount of energy releases is extremely small. The sun, being extremely hot radiates a great deal of energy across a wide spectum from extremely low frequency (something like the amount of heat you can feel if you hold your hand close to a glass of warm water) all the way to x-rays. However, our atmosphere is only transparent to a range from low frequency infra-red to fairly sort ultraviolet.
All matter will absorb some frequencies and reflect others. Plant leaves absorb much of the sun’s spectrum and use its energy to live and grow. The leaf reflects much of the green part of the spectrum so we call it green (not red).
There is really no such thing as “black light”; what we call that is merely a light source that puts out ultraviolet that we can’t see.
If you use a source with a red filter and shine it on a leaf, the leaf will appear black because there’s nothing for it to reflect.
Occam

So, the leaf is green.
It is not the color we do not see because it absorb that color and reflects the colors it is not. That thought would be incorrect.
I was not sure how that worked, everything could be gray and only had color when light was on it. and animals that only see in black and white were missing the ability to process the different wave lengths.
Never could get a handle on how that all worked.
Now the “red filter” removes all red light, is that correct, or does it only shine red light?

You can’t play games and try to define the color of something by what it reflects or by what it absorbs. We have the standard by general agreement that the color something (that’s not also a transmitter) reflects is the color we call it.
No, everything is not gray just because there’s no light shining on it. If there’s no light shining on it, you can’t see it so you can’t define any color for it.
We have ocular nerves that are triggered by light (rods) and nerves that are triggered by certain wavelengths (cones). Some animals don’t have the cones, and some can recognize more light differenations than we can.
No, By red filter I meant something like a glass sheet that allows light in the red area of the spectrum to go through but blocks (is opaque to) all other parts of the spectrum.
Occam

This is great information and to the point.
[If you use a source with a red filter and shine it on a leaf, the leaf will appear black because there’s nothing for it to reflect. ]
What happens to the red light. is it absorbed into the leaf?

Nice job Occam. Just a point of semantics really. The rods respond to light of all wavelengths in the visible spectrum and are only capable of measuring brightness. Therefor if we only had rods we would only see black and white. They are useful in dim light situations and critical to night vision since they are more sensitive to light than cones. That is why the world tends to look grey and less colorful when light levels are low. We have three different sets of cones which each respond to a more narrow spectrum of light. These three types cones allow us to see all the colors of the rainbow just like the Blue, Green, and Red dots are used to create all the colors you see on your TV.

This is great information and to the point. [If you use a source with a red filter and shine it on a leaf, the leaf will appear black because there’s nothing for it to reflect. ] What happens to the red light. is it absorbed into the leaf?
Its absorbed and turned into chemical energy and heat

Thanks, Mac. The eye structure and function have always fascinated me, especially the fovia centralis (no longer sure about the spelling since it’s been about 63 years since I took zoology and physiological psychology classes). Amazing that we can operate without any problem and not even be aware the blind spot without doing the dot and cross thing.
Occam

Mike, you might find interesting, a thread that I recalled from some time ago. Type in Primary Colors in the search box at the top of your page and go to that thread, and see what you think.

TimB,
Some of the same thought. First time I have used the search. Good tool.