Description: This demonstration shows the importance of resonance.
By sending powerful sound waves at the resonant frequency of the beaker, you can shatter it.
- Break the Beaker apparatus
- Function generator
- Mic with 9V battery
- Attach a 9V battery to the mic (this is needed).
- Turn on all the equipment. Make sure the Mic is CH2 and the function generator is CH1 on the oscilloscope.
- Make sure the function generator is set to -20dB attenuation if using the Samson amp.
- If using the Samson amp, connect the function generator as input 1 not in bridged mono mode (bridged mode is too much amplification). Connect the speaker to output 1.
- Set the oscilloscope to view the function generator (such as can be seen in the last picture).
- Prop the beaker up on the metal holder on top of the styrofoam. Point the lip of the beaker at the speaker.
- Aim the mic directly at the beaker and place it very close. Tap the beaker with the pencil and make sure you can view it on the oscilloscope.
- Try and tune the function generator to the resonant frequency of the beaker. Some fine adjustments will be needed in the classroom.
- Plug the apparatus in when in the classroom.
- When the professor is done, sweep out the broken glass.
- Take off the 9V battery.
- Place the pencil in the beaker.
- Turn the amp volume (left knob) up a little (not to break the beaker).
- Make fine adjustments to the function generator until you can get the pencil to vibrate.
- Take the pencil out, and fine tune the frequency by viewing the oscilloscope.
- When you quickly turn the speaker up a bit and then off, you should see CH2 resonant for a second or two after the speaker is turned off. This means you are in tune.
- When ready to break the beaker, close the safety flap and warn students that this will make a loud noise.
- Quickly turn the volume up high then off. The beaker should break.
- Do not leave the speaker on for more then a second or two at most (or the speaker will break).
- If the beaker does not break, further fine tuning is needed.
- When finished, turn off all equipment.
High Noise Levels
Hearing protection is recommended.