(b) Shake the tube slowly from end to end, and the rocks will slide from
one end to the other.
(c) Shake the tube harder and faster so that you pump more energy
into the rocks. The energy level of the rocks grows as they bounce off the rubber at
either end of the tube.
(d) These rocks are so light they will not go through the rubber. Glue
the rocks together, and make one piece of rubber thinner. Continue shaking the tube,
and the rocks will burst through the weaker rubber. In much the same way, a laser
beam bursts forth from a laser.
(2) The laser system works in much the same way as the example of the
rocks in a cardboard tube. Remember that example and relate it to this basic laser.
(a) The laser rod. The part of the system similar to the cardboard tube
is called a laser rod. Some laser rods are solid and made out of glass-like materials
called crystals. Other types of lasers use hollow glass tubes filled with mixtures of
liquids or gases.