Re: [asa] Easy to show experiments

Burgy -

In One Two Three ... Infinity, pp.121-123, George Gamow describes a experiment which shows (& allows you to calculate) the minimum thickness of an oil film & thus implies the existence of a minimum size of oil particles - molecules, of course, not "atoms" in modern terminology. Briefly, get a pan of water completely level, stretch a straight wire over it in contact with the surface & let a drop of oil spead out on one side of the wire. Then slowly move the wire, spreading out the oil, till the oil film breaks. You can see when this happens by the change in reflected light intensity where the film has broken. (The intensity from the oily part is less because of the change in phase of the light at the oil-air interface relative to that reflected at the lower surface of the oil film.)

It sounds simple in theory but I tried it once with no success. A cubic mm would cover about a square meter & you'd would need a precisely level surface & straight wire over a distance on the order of a meter. OTOH I'm no experimentalist.

Shalom
George
http://web.raex.com/~gmurphy/
----- Original Message -----
From: "Carol or John Burgeson" <burgytwo@juno.com>
To: <asa@calvin.edu>
Sent: Tuesday, September 11, 2007 5:15 PM
Subject: [asa] Easy to show experiments

> On another subject entirely, I'm interested in showing to young
> elementary age children that
>
> (1) Atoms exist
> (2) Light is a wave
> (3) Light is a particle
>
> I have found a very simple way to demonstrate (2) -- look at a light
> source through the separation of two fingers (my baseball scarred fingers
> are especially good for this purpose). As the fingers come together, dark
> lines appear between them -- it is usually easy to see at least three of
> these. The wave argument follows.
>
> I have heard somewhere that an equally easy way to demonstrate (1) exists
> but I have not been able to find it. All the ways to show (3) seem to
> require experimental setups.
>
> Any ideas?

To unsubscribe, send a message to majordomo@calvin.edu with
"unsubscribe asa" (no quotes) as the body of the message.
Received on Tue Sep 11 19:20:04 2007