I started recently wearing sunglasses during my online classes as laptop screens started taking a toll on my poor eyesight (of course my physics teacher wanted it removed but that's beside the point).

I noticed on one occasion when I stretched my neck nearly 45 degrees towards my left, the screen went completely dark and I couldn't see a thing on my laptop. I thought that the battery must have died and so as I reached for my charger I saw the screen reappear. I also observed the same happening when I looked at the screen from the corner of my eye as I faced the left side of the laptop (from my peripheral vision). In the image the laptop would come towards the my right side, around 10-20 degrees.

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More interesting I noticed this does not happen when I try the same from the left side (160-170 deg). My glasses left eye lens couldn't replicate what his right brethren could

My initial thoughts were this was some trick by Rayban company to help drivers blocking the sunlight coming to the right side as the left one couldn't do the same. (steering wheel is at right side over here, so It makes sense to block light coming from the right lens)

But whats the principal here?


It sounds as if your sunglasses have polarized lenses. (Most sunglass manufacturers offer both polarized and non-polarized lenses.)

Polarization of light can happen in a variety of ways. There is an excellent tutorial here. Put simply, polarized sunglass lenses feature microscopic parallel "louvers" (like the slats on a window blind). These louvers block light waves oriented perpendicular to them in the same way a window blind may block direct sunlight while admitting ambient light. Thus the light waves reaching your eyes are, in theory, aligned with the orientation of the louvers.

When viewing the outside world through polarized lenses, you might notice little polarization effect other than reduced glare. But it's when you view other polarized surfaces through polarized lenses, artifacts become visible. These can range from a mottled (spotty) pattern visible on other surfaces (such as when you look at automobile windows with your glasses on), up to and including a complete screen blackout as you describe.

LCD screens (such as those on a phone, tablet, or laptop) are necessarily polarized because that's part of how LCD displays work. A brief discussion of this can be found here. As a result, using polarized lenses to view a laptop screen can certainly cause the dimming or blackout you describe. Here is a short video demonstrating this phenomenon.

It's curious that you only see this phenomenon with one lens. I suggest a brief experiment: Turn your sunglasses upside-down, so the left lens is in front of your right eye and vice-versa. The nose piece will be pointing upward and the temple pieces won't hook over your ears, so you'll have to hold them in place. Now rotate your head in the same manner you describe, and see if the same phenomenon occurs (which it should). If so, you have your answer: The orientation of the polarized lenses in your particular sunglasses and the screen in your laptop are causing this. If you do not observe the same effect with the lenses inverted, it's possible your sunglass lenses are polarized differently from one another ... although that's not the typical design.

I hope this helps.


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