[Vatsal]

Vatsal asked the Naked Scientists:
   
If i close my eyes 80%-90% and watch a source of light (moon,street light), why does there appear to be a light ray going straight "up" from the source, rather than in any other direction?

If not familiar, you can try it right now by looking at, say, a window and closing your eyes to see the vertical effect.

What do you think?

[RD]

If the ray only occurs when you squint it is probably the result of diffraction at the straight(ish) edge of your eyelid which is then over your pupil.

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