One of the nine jewels of Emperor Akbar, widely known as Tansen (the king of Music) , was able to break glass by singing appropriate note. What physical phenomenon could account for this?

One of the nine jewels of Emperor Akbar, widely known as Tansen (the king of Music) , was able to break glass by singing appropriate note. What physical phenomenon could account for this?
Ans: The physical phenomena involved in this trick is resonance. When the natural frequency of the glass coincides with the frequency of the singer’s voice, resonance occurs and when amplitude of the vibration becomes more than the breaking force, the glass cracks.