Date: Tue, 30 Nov 1999 09:59:35 -0500

Author: Tom Ford

Subject: Re: Optical Puzzler

Post:

At 04:10 PM 11/10/99 -0500, you wrote:
>
>Showing my ignorance here ... what's an OHP?
>
>Anne

Sorry, I thought the context would give it away--
Over Head Projector
There is always this danger in using an acronym without explicit definition.

>
>Tom Ford wrote:
>
>>
>>
>> Turn on the OHP (best if the lens is folded away or removed), place the
>> aperture in the very center of the stage, place the container -- nearly
>> full of water -- in the center of the aperture. Notice the very bright spot
>> on the ceiling in the center of a narrow bright ring and -- further away
>> from the spot-- a "rainbow" that is red side inward. Notice that the bright
>> central spot seems about the same size no matter how far away the
ceiling is.
>>
>>
>
>

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