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?
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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.
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