If a simple
lens that is thicker in the middle than on the edges is held close to
an object, the image appears magnified and enlarged. This simple
magnifier is the most common use of a simple lens. Another
common use of a simple lens is to view a distant object shown in PPOW
of November 30, 2007.
Unlike the real inverted image when the lens is held at arm's length to
examine distant objects, the image produced by the simple magnifier is
a "Virtual" image. It doesn't cast light onto a screen. The
location of the virtual image is behind the lens. Actually it is
further away than the object although the photograph doesn't prove that.
liquid also make simple lenses. The surface tension of a drop of
liquid on a glass surface causes the top of the liquid to be
curved. Since the liquid has a refractive index, the curved
surface forms a simple convex lens. The picture at right was made
by placing a drop of honey on a piece of glass. The glass was
placed on a textbook-sized copy of the Periodic Table of the
Elements. The drop of honey forms a similar magnifying lens to
magnify the atomic mass of Si - the most abundant element in Earth's
crust. Honey was much more effective than water to make this
demonstration for two reasons: it has a high refractive index or
refractive power, and it stays "beaded" up to form a convex shape on
the top section as in the drawing below.
Photo of the
published weekly during the academic year on Fridays by the Warren
Wilson College Physics
Department. These photos feature interesting phenomena in
the world around us. Students, faculty, and others are invited to
submit digital (or film) photographs for publication and
explanation. Atmospheric phenomena are especially welcome.
Please send any photos to firstname.lastname@example.org.
All photos and discussions are copyright by Donald
Collins or by the person credited for the photo and/or
discussion. These photos and discussions may be used for private
individual use or educational use. Any commercial use without
written permission of the photoprovider is forbidden.