This demonstration is similar to Laser Sine Wave from Tuning Fork, but the tuning fork is now driven by a magnet coil connected to an audio oscillator. Normally the beam is not scanned with the rotating mirror, but one merely observes the amplitude of oscillation on the wall. One can demonstrate resonance by observing the large increase in amplitude when the oscillator is tuned to the natural frequency of the fork. If the oscillator is tuned slightly off resonance, beats between the driving frequency and the natural frequency are observed.