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APPARATUS

This is similar to the beaker breaker but requires less sound volume and lower frequencies. With the pane of glass of length L supported 0.224L from each end, vary the function generator frequency around 50 Hz to find the resonance frequency of the glass pane. The glass can be seen to flex. Turn up the volume to break the glass.

Use a piece of glass about 24" x 3" and no more than 1/8" thick.  Mark the center and 0.224L from each end.

Find and record the resonance frequency.  The expected frequency for a bar with free ends is f₁ = 1.028 a/L² √(Y/ρ) , where a = thickness, L = length, Y = Young's modulus, and ρ = density (see http://hyperphysics.phy-astr.gsu.edu/hbase/Music/barres.html). 

If using the strobe, set it to just above or below the resonance frequency.

The box should be level enough that the glass doesn't creep off.

REFERENCE

 

http://www.personal.psu.edu/ref7/apparatus/2006%20competition/kardelis.htm