Re: Virtual and Real Images

["Paul O. Johnson" <pojhome@SWBELL.NET>]

----- Original Message -----
From: "Hugh Haskell" <hhaskell@MINDSPRING.COM>
Sent: Tuesday, 19 March, 2002 10:48
Subject: Re: Virtual and Real Images

> That a real image can exist in space even without a surface for the image
to
> be realized on can be demonstrated in several ways. One is to darken
> a room, project a slide into space (i.e., no screen at the location
> of the image, and then rapidly move a broomstick across the light
> beam at the point where the image should be. The viewers will see the
> image appearing on the broomstick, and because of the persistence of
> vision, it will appear to be an entire picture.

Now hold on thar, Hugh. We have such a projection exhibit at The Science
Place in which explorers swish a white 3/8-inch dowel up and down. But there
is no "point where the image should be". Because of the depth of field of
the projector, they can swish the dowel at almost any distance from the
projector and see a focussed image on it. The closer to the projector they
stand, the smaller the image is.

poj