Microscopes, binoculars, cameras,
and telescopes form images by refracting light or by reflecting light.
The key difference between refraction and reflection is shown below.
Refraction occurs in when light enters a transparent material.
Light slows down and changes direction - different wavelengths of light
are affected by different amounts - shorter wavelengths are slowed more
and their direction changes more.
The animation below shows this effect
(file source http://en.wikipedia.org/wiki/File:Light_dispersion_conceptual.gif
).
This effect tends to spread out the different wavelengths of
light.
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