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Re: Test Writing



-----Original Message-----
From: Herbert H Gottlieb [mailto:herbgottlieb@JUNO.COM]
Sent: Tuesday, April 30, 2002 12:43 PM
To: PHYS-L@lists.nau.edu
Subject: Re: Test Writing

[snip]

1. You cannot always see a real image. The real images that
are formed
by
a convex lens or a concave mirror are usually invisible. To
see such an
image it is necessary to place a screen at the position that the image
forms . If a screen is not placed at the image position ,
the image is
still formed there .... but it is invisible.

2. You can see a virtual image. Just look into a plane
mirror and there
it is!

I know you wrote "usually invisible" but I think it is important to note
that a real image is invisible only if you aren't looking at it. As long as
you are looking "through" the lens/mirror (or you bounce the light off of
something) and the real image is in front of you, you should be able to see
it.

The same is true of a virtual image.

____________________________________________
Robert Cohen; rcohen@po-box.esu.edu; http://www.esu.edu/~bbq
Physics, East Stroudsburg Univ., E. Stroudsburg, PA 18301