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This isn't your typical water damage story.

One side of my 2007-model, pre-Unibody laptop got damp from rain in a backpack yesterday. When I opened it, the left quarter of the screen had a splotch of water damage.

The damaged area is brighter and more vibrant than the rest of the screen!

The "damage"

The screen has seemed dim for most of the laptop's lifetime. Not long after its first birthday I even disassembled the screen looking for the problem. I found a blown capacitor and supposed a backlight power issue, but later discovered that wasn't the case.

Now this seems to confirm it's some kind of optical effect. But what? I know plenty about optics and this doesn't make sense. The water must be filling a gap and providing better coupling between two layers, but there's no brightening if I press lightly on the screen. There's a little thin-film interference at the edges of the water layer where it tapers off. So the water layer is doing something.

The laptop will be fine in a few days; the water seems to be evaporating out through the screen. But I'm suffering this physics mystery.

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lol, then you sure this question is suppose to be on apple stackexchange then? XD –  theAmateurProgrammer Jul 24 '12 at 5:28
    
@theAmateurProgrammer This is my first question. Perhaps it belongs on Physics. I've never asked anything there, either. –  Potatoswatter Jul 24 '12 at 6:13
    
You're asking what kind of optical effect does water have on the brightness of the screen, and not apple related. –  theAmateurProgrammer Jul 24 '12 at 6:15
    
@theAmateurProgrammer Most likely this effect is peculiar to this LCD. –  Potatoswatter Jul 24 '12 at 6:16
    
congrats for a partially nicer screen? –  revolver Jul 24 '12 at 8:39

2 Answers 2

up vote 4 down vote accepted

The reason it's brighter is because water has a refraction index that is closer to 'glass' (as in the specific material used in the screen--I know it's not really glass per se) than air does. This means that less light is lost in the area between the LCD and the front glass (or between the LCD and the backlight--but not very likely) and thus the screen appears brighter.

You'd probably get a better explanation on Physics in terms of specifics, but this is the answer in a nutshell.

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Yes, but why is an air layer even there, and in that case shouldn't pressing on it also remove the air? I'll select this since it's clearly got something to do with it, but I think there's something else, perhaps a defect. –  Potatoswatter Jul 25 '12 at 3:39

I have noticed the same effect when using a flatbed scanner to scan samples of wood (I dabble with tree-ring research). I get better results when I put a layer of water between the wood and the scanner plate. A colleague told me I would get even better results if I used oil - but I didn't want to foul up my scanner, so I didn't try that. I wonder if a layer of mineral oil would allow you to retain your screen improvement indefinitely.

I would like to propose that the layer of liquid effectively 'smooths out' the surface of the LCD and the underside of the screen, resulting in less scattering of light(?). In support of this idea is that the smoother the surface of my wood samples, the clearer the resulting scan (for example with finer and finer sanding). I think this effect could be working in tandem with the Refractive Index effect explained by Matt above.

Can you report back, did your screen dry out without failure in the end? I'm curious, because I half-filled my Macbook Air screen with water last week. It seemed to work fine during the shutdown sequence, but I have been hesitant to turn it back on again until it dries out completely.

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The screen is still drying out to this day. Instead of improving light transmission, it's now a very thin layer of water, on the order of the light wavelength. The spots therefore look dark. If I recall my research, touch screens usually have everything bonded to the glass but other LCDs have air inside to this day. It's probably hard to reliably trap a liquid layer. Good luck with your Air, I don't know what advice to give… –  Potatoswatter Jul 25 '13 at 12:12

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