BACKGROUND:
There are two major
types of waves, physical waves and electromagnetic waves. Sound waves
are physical because they actually have a physical motion in the surrounding
area. Light is an electromagnetic wave which will be discussed in
detail in the 5th grade physics lesson. Waves represent a mechanism
whereby energy is transmitted.
Sound is heard because of vibrations.
Vibrations are a disturbance of the air space that mechanically moves the
air. Sound cannot travel in a vacuum because there is no medium.
Sound travels in a push-pull or compressional type of manner. Introduce
the word "pitch." A pitch is the "highness" or "lowness" of a tone,
governed by frequency. High frequency equals a high pitch sound,
while low frequency equals a low pitch sound.
When a rubber band is stretched
a little and strummed, it will cause little vibrations and a low pitch.
If you stretch the rubber band further and strum it, they will have
created a higher pitch.
PROCEDURE:
- In this experiment,
students will establish that sound needs a medium to be transferred.
Students are asked to see if the sound produced by a tuning fork can be
felt or heard by hitting the tuning fork and touching it to the nose, hand,
nail, paper, pencil, pen and cup of water.
- Students should feel
a "tingling" feeling when the tuning fork's tines touch their bodies.
The nose is the most sensitive. The nail, pencil, and pen will just
vibrate. The papers should give a humming sound. The vibrating
tuning fork sets up vibrations in the water. The spot where the tuning
fork hits the water is similar to the focus of an earthquake or the point
where a pebble enters the water.
- In the next activity,
students are asked to look at 6 similar jars and fill them with different
amounts of water. Different amounts of water in a jar will produce
different sounds. Students should only use a stick or pencil to tap
the jars, and then record their findings. The more liquid in the
jar, the lower the pitch. Have students arrange the jars from lowest
to highest pitch.
- Students have learned
that sound is a physical wave and is transmitted through substances in
different ways.
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