For example, glasses for red-green color-blindness filter out yellow, so it’s like a blue filter, but wouldn’t that only worsen the problem, for red, yellow, and green are not visible at all?
In: Engineering
Normally, people’s eyes have three color receptors, for red, green, and blue light.
However, there’s some overlap. Orange light, for example, will excite both the red and the green receptors a little bit. For some people, *red* light will excite both the red and green receptors, which is a problem because then it seems really similar to when orange light is received, since both receptors respond similarly.
The glasses take out a section of light that’s most overlapped. This means that a chunk of the red and a chunk of the green light is simply filtered out, but *some* of the red light (the “redder” light) remains, and *some* of the green light (the “bluer” green light) remains.
As such, when someone wearing the glasses sees a red balloon, they’ll only see the reddest light coming from that balloon. So it will appear definitely red. Whereas when they see an orange balloon, it will no longer make the red receptors respond since the reddest light from the orange balloon will have been filtered out, allowing the green receptor to respond a little bit to it, and the red receptor to respond a little bit to it (due to the orange balloon still having *some* red light that gets through on the reddest side of the spectrum) and so the orange balloon can be seen as distinct from the red balloon.
Meanwhile, blue balloons look blue, since they never had as much red or green light reflecting from them to begin with.
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