Learn about resonance in this video adapted from the Encyclopedia of Physics Demonstrations. A demonstrator taps a glass beaker to find its natural frequency of vibration and then sets an oscilloscope and amplifier to produce a loud sound at that same frequency. The resonance created by exposing the beaker to the sound wave forces the glass to vibrate and distorts the shape of the beaker. The amplitude of the sound wave from the speaker is increased until the oscillation of the beaker exceeds the elastic limit of the glass and the beaker breaks.