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I'm no scientist and unfortunately my municipal IT filters haven't let
me view the diagram, but one possibility is that the diagram does not
include the change in image that occurs within the lens itself. Don't
the "light rays" refract within the lens and re-refract departing the
lens to get larger or smaller, depending on the curvature and thickness
of the lens? Then, in a telescope, the second lens not only focuses, but
(again, depending on shape) makes further changes (or no change if
symmetrical) in the size of the image.
John Elliker
Nauticus
One Waterside Drive
Norfolk, VA 23510
757.664.1033
-----Original Message-----
From: Informal Science Education Network
[mailto:[log in to unmask]] On Behalf Of David Savory
Sent: Thursday, September 10, 2009 11:46 AM
To: [log in to unmask]
Subject: Re: Subtle telescope details
ISEN-ASTC-L is a service of the Association of Science-Technology
Centers
Incorporated, a worldwide network of science museums and related
institutions.
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*****
I'm starting to wonder if this is one of those diagrams like the tongue
"taste regions," or the "we only use 10% of our brains" business,
frequently stated but wrong in some subtle, fundamental way.
I think the problem is with ray diagrams that are not exactly wrong but
are so abstract they create a retrograde confusion: they mess up things
previously understood. This is not good. Most kids (most people!) have
no clue what the arrows represent, something moving but what, photons?
Why aren't there more of them?
A better way to go is to give kids some lenses, make some observations
and try to come to some conclusions. Then proceed with future inquiries
and explanations on the basis of their terms and conceptions, not those
of an expert physicist.
David Savory
Community Extensions Program Developer and Exhibit Curator
Science World British Columbia
TELUS World of Science
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Vancouver, BC
Canada V6A 3Z7
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