

A laser experiment to show the Uncertainty Principle [video] - hhm
http://www.youtube.com/watch?v=KT7xJ0tjB4A

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noonespecial
I love his old school HeNe Laser! Takes me back.

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huhtenberg
If you don't know who Walter Lewin is, have a look here -
[http://en.wikipedia.org/wiki/Walter_Lewin_Lectures_on_Physic...](http://en.wikipedia.org/wiki/Walter_Lewin_Lectures_on_Physics)

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foonamefoo
As the slit gets smaller the percentage of photons that are bouncing off of
the walls of the slit as compared to the percentage that goes through directly
raises.

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yummyfajitas
True, but geometric rays of light bouncing off the walls of the slit won't
broaden the beam. Similarly, the barrel of a machine gun doesn't broaden the
stream of bullets coming out.

Only Heisenberg does (note, however, this is a purely classical/maxwellian use
of Heisenberg).

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anewaccountname
Right, but it is interesting that if the camera were adjusting it's iris due
to the decrease in light, we would see the same thing without Heisenberg. The
spread would be there in both cases, but would be overwhelmed in the wide-open
case by all of the particles of light making it straight through. As the light
intensity lowered and the iris widened to compensate, the effects of the
photons bouncing off of the walls of the slit would begin to be more visible.

