Resonance

vibration · physics · sound · energy

Musical magic. When you pluck a guitar string, the air around it vibrates at the same frequency, making the sound louder and richer. This is why hollow instruments like guitars and pianos sound so much better than a vibrating wire alone.

Bridges can wobble. If soldiers march in perfect step across a bridge, their rhythm might match the bridge's natural vibration frequency, causing it to shake dangerously. This is why marching troops are told to break step when crossing bridges.

Radio stations tune in. Radio receivers use resonance to pick out one specific station's frequency from all the radio waves floating around in the air. By tuning to the right frequency, your radio's circuits start vibrating at that exact speed and catch that station's signal.

Pendulums love rhythm. A pendulum swings best when you push it at just the right moment in its swing. If you push at the wrong time, the pushes work against each other, but at the right time, each tiny push adds up to bigger and bigger swings.

Wine glass sings. If you make a sound at exactly the right pitch near a wine glass, the glass will vibrate so hard it can actually shatter. Opera singers can do this because their voices can reach that perfect frequency.