Bell Jar [Virtual Demonstration]

In space, no one can hear you scream.

We put the famous tagline from Alien to the test in this demonstration. It's the classic bell jar in which a bell in a bell jar is subjected to a high vacuum as we listen for the sound.

The Encyclopedia Britannica Education Corporation's (EBEC) "Learning About Sound" 2nd Edition, 1974 filming of this demonstration was masterfully executed. 

• Smoke is added to the bell jar prior to evacuation so that the air can be seen. And that smoke is thick! When it's gone, the air is essentially gone.

• The microphone (sound detector) is placed inside the bell jar, so no need to worry about any impedance mismatch preventing sound from escaping. The sound is being detected inside the jar.

• After the vacuum is achieved, air is allowed to re-enter the jar while the bell continues to ring.

The EBEC footage was saved and restored in Ztek's Physics: Cinema Classics (P:CC) project.

If you can run the demonstration effectively in class, do it! I could not, so I used this version. When remote teaching/distance learning (RT;DL) kicked in, updated it to this.

Bell Jar [Virtual Demonstration] at Teachers Pay Teachers

I don't hold the copyrights to the stills and clips in the linked presentation, so this one is Fair Use free. As always, it's print-friendly Google Docs student document and answer key files, located on Google Drive for convenience.

Oh, and I added this resource to the Bundle of Phyz: WAVES AND SOUND. I think I might have a few more items to add to that bundle now that I'm thinking about it. My "Connect the Dots" lab and "Moving Sources" P:CC video demonstration.