Turntable with mirror and needle attached to tracking arm, laser
needle attached to tracking arm

 

Code Number: 3C20.23

Demo Title: Grooves on a Record - LP

Condition: Good

Principle: Mechanical Vibrations Converted to Sound.

Area of Study: Oscillations &Acoustics

Equipment: 

Turntable with mirror and needle attached to tracking arm, laser.

Procedure:

Place the LP record onto the turntable.  Place the needle on the 4th track of the E. Powers Biggs record and align the laser to reflect off the mirror and onto the opposite wall of the lecture room.  The vibrations of the needle as it moves over the grooves at constant speed are shown with the large amplitude vibrations giving the largest movements of the laser beam on the wall. 

References:

  • Alaina G. Levine, "A Sweet Sound: Physicists Reconstruct Primitive Recordings", March APS News, March 2015, Vol. 24, # 3, p. 3.
  • George M. Hopkins, "A Simple Phonograph", Experimental Science, p. 149.
  • Guinness World Records, "Smallest Functional Vinyl Records", 2003, p. 112.
  • Stan Horaczek, Jon Enoch, "For the Records", Popular Science, Winter 2019, p. 26.