Demonstrate that sound waves require a medium to travel in. Classes Used: PHYS 101, 153

Show that sound waves require a medium to travel in

Bell jar containing alarm and pressure gauge/valves Vacuum pump

Attach pump hose to nozzle Open intake valve and close outlet valve Turn on the alarm via the switch Turn off alarm and turn the pump on to evacuate the jar Turn alarm on again to demonstrate it has gotten much quieter Release outlet valve while alarm is on to show how it get's loud again

You will still hear a little noise from the alarm due to vibrations and the limits of the vacuum pump Valves are open in the vertical position (perpendicular to the pipe) and closed in the horizontal position Updated on: 06/19/13