Yesterday I clicked on Phil's Blog announcement of the discovery of Pluto's new moons. To my amazement I could see 'Haidinger brushes' in the white area of the page (where there is no print).

At first I thought I had some sort of yellow smudges on the screen of my laptop. Upon closer inspection I could see the characteristic yellow hour-glass shape and realized I was starring at the illusive 'haidenger brushes'!

Has anyone ever seen them ON THEIR LAPTOP??!
THis is the first time I've ever seen them even though I have tried before (unsuccessfully) to see them against a diffuse blue sky.

However, this begs the question:
Does a laptop computer screen emit circularly polarizd light???

puzzeling....
Gsquare

Seeing Haidinger's Brushes

I can't say I've ever noticed.

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I had to google this. I learn something everyday.

So the laptop DOES have polarized emissions; thanks for the link!


Well, I never have either, and I still don't notice "haidinger brushes" on any other web pages or backgrounds on my laptop.
The strangest thing is that I can only see it on Phil's blog page on Pluto
located here: http://www.badastronomy.com/bablog/?p=199

The image 'follows' my line of sight on the page and is about 1.5 inches across. And curiously, when I tilt my head the 'hour-glass' tilts also, but
it tilts at about two to three times the angular rate that I tilt my head. Strange.
Why would tilting my retinas 30 degrees cause the image to tilt 90 degrees?

It may be possible that there is something in the background of that blog that allows my computer screen to bring out enough polarized light so that my eyes can perceive the brushes.
See if you can see it on Phil's blog.

Gsquare

Nope. I see nothing unusual about that blog page by way of polarization (using a laptop with LCD screen).

I did pul out a kind of polarizing filter to view it and nothing unusual happened.

But, that did cause me to discover another amazing property of my filter -- which I guess is a circular polarizer, from reading a description on the Web. I got it a long time ago, as a freebie, and best I can recall it is a linear polarizer sandwiched to a quarter-wave filter at 45 degrees. When you look at normal lights, either direction, it just seems like an amber filter. It does have a sunglass-type reflection suppression because of the linear filter -- when light goes through it one direction.

The confounding thing I amazed friends with was letting them hold it in front of an eye and look into a mirror. One way, what you see is your amber reflection, with an amber filter over the eyeball. That's the case of light striking your face, going through the quarter-wave layer, going through the linear polarizer, striking the mirror, coming back through the linear polarizer, through the quarter-wave and onto the retina.

But, when you flip the filter over, you still see your amber reflection, but now the filter's reflection looks totally black. Light strikes your face, goes through the linear polarizer, goes through the quarter-wave layer (getting a 45-degree twist), strikes the mirror, comes back through the quarter-wave (getting another 45-degree twist, total 90) and now cannot penetrate the linear polarizer.

Magic tricks are readily availble if you disguise the flipping of directions or your mark doesn't notice. It's just counterintuitive that a view could be different depending on the direction light takes through a hunk of plastic.

Another good demo is just to place it on any specular surface, a small mirror, a coin. One way, it just colors the reflecting object amber. The other way the object looks black.

So, I hadn't known about an LCD producing polarized light. It is indeed a good source. Holding my filter up to it one way, quarter-wave toward the screen, it's just amber light no matter how you spin it. Flipped over, linear polarizer toward the screen, it's amber light one way, but black at 90 degrees. Cool, cheap fun.

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Yes, Candy; That's just about what it looks like, except I can't see the two little greenish spots in the hour-glass.

Has anyone else seen these slippery slueths?

G^2