BACKGROUND:
When light hits a surface, part
of the light is reflected. On a clean and polished metallic surface
almost 100 percent of incident light is reflected, while on a surface of
clear glass only a small amount is reflected. When light bends as it
passes from one medium to another, this is called refraction. PROCEDURE:
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Draw the following
diagrams on the board to illustrate both principles.
In the
kaleidoscope that students made, reflection produces the images. Not all
flat surfaces reflect as well as others. Aluminum foil in a kaleidoscope
does not work as well as Mylar because aluminum is not as reflective as
Mylar. Mylar is not as good as a mirror which has a backing of a silver
compound.
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Introduce how
different lenses can move light by either refraction or reflection.
Different lenses can control the type of picture we take or even how we
see. Go over the different shapes of the lenses as shown in the
worksheet. Introduce the terms biconvex, biconcave, plane convex, planar
concave, meniscus convex, and meniscus concave which just refer to their
shape.
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Instruct students
to try and figure out how light will react in each of the different
situations. Remind students to look for a mylar surface. This will
determine whether the light is reflected or refracted. The color and the
clarity of the lens also determines if all light passes through or if
some is refracted.
ANSWERS:
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