Eli5: Why are blue light signs so grating to the eyes in comparison to red light signs? When I’m on the road red signs feel more easy on the eyes for some reason?
In: 9
You’re absolutely right! Blue light is more straining to the eyes. It has to do with light waves (how light photons travel). Light travels just like radio waves. Red light travels at a lower frequency than blue light. Since blue light is a higher frequency the photons are hitting our eyes much more frequently and more intensely causing strain and even discomfort to your eyes. This is why computers and phones have the option to turn on blue light filters.
It’s a complicated topic, but one of the reasons is because blue light has more energy than other colors. While purple has even more energy than blue, a lot of purple is invisible because of UV. Older blue lights weren’t as bright because they were incandescent lights with a blue filter, rather than true blue light.
Blue light is hard on the eyes. It’s something that’s only recently been studied since in the past blue light was hard to come by. Now we have blue light all over the place, most commonly in computer, TV, and phone screens. It’s basically the reason we experience “screen fatigue” when we stare at bright screens all day.
Many devices now have a “blue light filter” or an “eye comfort” mode to help. You can also buy a pair of blue light filtering glasses (~$20 on Amazon) that I’ve personally found to work wonders.
Red light also doesn’t damage your night vision as much as other colors. This means that your pupils aren’t constantly expanding and contracting due to the presence/absence of red light.
The actual answer has nothing to do with blue light having more energy, and certainly not that photons are hitting your eyes more often. it’s kind of counterintuitive, but light with a higher frequency is described by higher energy photons, not more photons per second. more photons per second would make the light brighter, not change the wavelength.
the real reason blue lights are hard to look at is that shorter wavelengths of light get bent (i.e. refracted) more severely when they pass through something transparent (i.e. the lens of your eye). this is the reason that prisms split light into different colors – white light enters the prism, and then the blue light leaves at the sharpest angle, red leaves and the shallowest angle, and the other colors are somewhere in between. because lenses focus light by bending it, any lense will focus different colors at slightly different distances. blue and violet light, because they refract so severely, have a focal point that is furthest away from your retina, making them blurry and uncomfortable to look at as your eye tries to compensate.
Latest Answers