文档介绍：PP UZZLERUZZLER
A simple seismograph can be con-
structed with a spring-suspended pen
that draws a line on a slowly unrolling
strip of paper. The paper is mounted on a
structure attached to the ground. During
an earthquake, the pen remains nearly
stationary while the paper shakes be-
neath it. How can a few jagged lines on a
piece of paper allow scientists at a seis-
mograph station to determine the dis-
tance to the origin of an earthquake?
(Ken M. Johns/Photo Researchers, Inc.)
chapter
Wave Motion
Chapter Outline
Basic Variables of Wave Motion Reflection and Transmission
Direction of Particle Sinusoidal Waves
Displacement Rate of Energy Transfer by
One-Dimensional Traveling Sinusoidal Waves on Strings
Waves (Optional) The Linear Wave
Superposition and Interference Equation
The Speed of Waves on Strings
490
Wave Motion 491
ost of us experienced waves as children when we dropped a pebble into a
pond. At the point where the pebble hits the water’s surface, waves are cre-
Mated. These waves move outward from the creation point in expanding cir-
cles until they reach the shore. If you were to examine carefully the motion of a
leaf floating on the disturbed water, you would see that the leaf moves up, down,
and sideways about its original position but does not undergo displace-
ment away from or toward the point where the pebble hit the water. The water
molecules just beneath the leaf, as well as all the other water molecules on the
pond’s surface, behave in the same way. That is, the water wave moves from the
point of origin to the shore, but the water is not carried with it.
An excerpt from a book by Einstein and Infeld gives the following remarks
concerning wave phenomena:1
A bit of gossip starting in Washington reaches New York [by word of mouth]
very quickly, even though not a single individual who takes part in spreading it
travels between these two cities. There