Final answer:
An opera singer can shatter a crystal glass by singing a note that matches the glass's natural frequency, causing it to resonate and vibrate until it shatters.
Step-by-step explanation:
The trick of an opera singer shattering a crystal glass works due to resonance and the natural frequency of the glass. The performer must sing a note that matches the natural frequency of the glass. When the sound wave from the singer's voice is directed at the glass and matches its natural frequency, the glass begins to resonate and vibrate. With enough energy introduced into the system, the glass eventually shatters.