Tuning Fork
Basics
It’s important never to bang a tuning fork directly on a hard surface, as this
could damage the tuning fork. Instead, grasp it firmly at its end but keep your
wrist and fingers relaxed. Bend your elbow when holding it. There shouldn't be
any tension in your arm. Hold the tuning fork on its side so you're striking only
one of the prongs. Tap it against the heel of your hand or a rubber object. It’s
made of dense metal, usually steel. Strike the tuning fork prong about one-third
of the way from the top. This is important to get the best sound. The "U" shape
causes both sides to vibrate and produces a smooth sound wave.
Visualizing Waves Tap the tuning fork against the heel of your hand, and look
closely at the tips as the fork hums. You'll notice the tips are vibrating very
slightly. This is a simple activity, but it clearly demonstrates sound waves in a
visible way. Try a variety of tuning forks, and see if you notice any difference in
their vibrations.
Wave Transfer Sound waves and energy transfer through various materials
differently. Have one partner sound a tuning fork and hold it in the air while the
other partner walks away until he/she can't hear it any longer. Measure the
distance. Strike the tuning fork again and set the vibrating tuning fork carefully
on a hard surface like a desk or a chair seat. This acts as a sounding board and
amplifies the pitch. Next, using a metal rail or pipe or a wooden banister, tap
the tuning fork again and then place the base of the tuning fork against the
metal rail. Put your ear on the rail. Repeat the process for the wooden banister.
You'll notice the sound waves travel to a greater or lesser degree depending on
the material air, metal or wood.
Water Tray Sound a tuning fork, and place the tips lightly on the surface of
some water. Watch how the water reacts to the sound waves. Try the same thing
with the end of the handle, and see if it reacts differently.
Feeling Sound Tap the tuning fork again, and place the bottom of the handle
against your cheekbone, just ahead of your ear. It will feel weird for a second,
but you'll notice that not only do you hear the sound?, you can feel the
vibration? How does this compare when you use a different tuning fork?
Adapted from lessons in Targeting Students Science
Misconceptions and Invitations to Science Inquiry
Tuning Forks and Air Columns
(resonance)
Materials for each group 2 tuning forks
Cylinder with two open ends and a dish of water or
identical 4 bottles with water (empty, ¼ full, 2/3 full
and filled)
pieces of wood, metal and plastic
Procedures
Part I
1. Predict the difference, if any, in the sound generated by a tuning fork
when it comes into contact with wood, air, metal, plastic and glass.
Explain the reasons for your prediction.
2. Have a member of the group share your predictions with the rest of the
class.
3. Test the prediction and explanation by listening to the sounds generated
by striking and placing a tuning fork on wood then metal then plastic and
then glass.
4. Discuss your observations and compare them with your predictions.
5. What statement(s) can you make about the sound generated by striking a
tuning fork and placing it in contact with different materials?
6. Share your combined statements with the whole group.
Part II
1. Predict what will happen when you hold a vibrating tuning fork above an
open cylinder or empty bottle.
2. Test your prediction.
Adapted from lessons in Targeting Students Science
Misconceptions and Invitations to Science Inquiry
3. Observe and compare your findings with your prediction.
4. Lower the cylinder into water while holding the vibrating tuning fork
above it and note what happens or hold it above the different flasks with
water noting the differences.
5. Add water to the cylinder or glass bottle until the emitted sound is the
same as from the tuning fork. What caused the sounds to match?
6. What additional questions or investigations do you have to pursue with a
tuning fork related to transferring vibrations?
Adapted from lessons in Targeting Students Science
Misconceptions and Invitations to Science Inquiry