Thread: I am confused

the ability for humans to see light (and colors) is limited between UV and infrared
all colors have a certain frequency within this frequency band of visible light.
It is said white light is the occurance of the complete band (all frequencies between UV and infrared are there)
all colors can be made by mixing three colors (red, blue, green)
as these colors represent a single frequency in the visible band, it doesn't make sence...
mixing frequencies should result in the original frequencies and their sum and substracts being present in the resulting color.
by changing the amplitude (intensity) of the three main colors, it shouldn't result in a variety in colors (frequencies) but only change the spectrum
mmm... I am not sure I cornered the root for my confusion...

Mixing colors does not produce additional frequencies. It is just perceived that way by the human eye because of the degree to which the three types of color sensing cones are stimulated.

As a consequence of what Harold has said, if you used a detector to analyse ('see') the spectrum of white light and the light reflecting off the rotating disc it would show distinct differences.

Originally Posted by 3s

mixing frequencies should result in the original frequencies and their sum and substracts being present in the resulting color.

You have to be careful with the terminology. Indeed, there are electronics called "mixers" that allow the production of sums, multiples and other kinds of frequencies. Those tools are e.g. used as heterodyne receivers in radio astronomy. But this is not how the eye works. The white "colour" is a result of the superposition of the effect of every single frequency that hits the retina. The mixture of individual colours is then interpreted as "white" by the brain.

well indeed, thats what I am referring to the superheterodyne principal used in modulators/demodulators.However same principal exists using waves with different frequencies (like for example audio waves).Mixing should be seen in a wider context, like being present at the same time at the same place.
so light being a wave of a certain frequency (depending on the color), it answers to the same laws of fysics (heterodyne), however the sum or substract of any two colored lights will result in frequencies outside the visible band
from the repplies, I should conclude that all colors can be made using only three colors, as the eye withholds receptors, sensitive for those three frequencies only
but on the other hand that same color could be achieved using a tunable laser, emitting only a single frequency specific for that color

Originally Posted by 3s

from the repplies, I should conclude that all colors can be made using only three colors, as the eye withholds receptors, sensitive for those three frequencies only

To be more precise, the receptors have a peak sensitivity to a certain wavelength, but are capable of responding to a spectrum of wavelengths. If not, we would only see three colors in a rainbow, rather than a continuous spectrum.