Applications of Concave Mirrors
One
very important application of concave mirrors is in the familiar
"satellite dish". These antennas are designed to receive and amplify
weak signals sent from communications satellites in space. Since
these satellites are so far away, the waves that reach the earth from
them are practically parallel. When these waves strike a
properly-aimed concave mirror, they are all reflected through the
focus of the mirror. At the focus is placed the receiver for the
signals. The purpose of the mirror is to gather the weak signals over
a large area and concentrate them in one spot.
Another example of the practical application of concave mirrors is
the headlights of your car. A small but powerful light source is
placed at the focus of the concave mirror that forms the back of the
headlight. Any light from the focus that strikes the mirror will be
reflected parallel to the axis of the mirror. This is how the
headlight beam is formed.
Another important application of concave mirrors is the astronomical
telescope. All large telescopes (and many small ones) use a large
concave mirror at the bottom of the telescope to gather light and
form a small image on a small plane mirror at the top. The purpose of
the plane mirror is simply to reflect the light into the eyepiece (or
camera or other instrument) of the telescope. Larger mirrors gather
more light, enabling astronomers to see fainter objects. Many people
not familiar with astronomy think that the enlarging power of a
telescope is the most important, but this is only true when you are
observing relatively nearby objects, like the moon or a planet. Stars
are so far away that they appear to be points of light - no matter
how much they are enlarged. A large astronomical telescope does not
enlarge the image as much as it enables one to see a fainter
image.
last update September 20, 1999 by JL
Stanbrough