- Slides: 11
Resonance and Standing Waves
Resonance • Every object has its own natural set of frequencies it will vibrate at when struck. • The frequencies depend on… – The size of the object – The material the object is made of – What the object is struck with
Resonance • A phenomena in which an object can be forced into oscillation due to an outside vibration at the object’s natural frequency.
Resonance scenario • Object 1 is not vibrating, but has a natural frequency of f 0. • Object 2 is struck and vibrates at f 0 nearby object 1. • The sound waves pass through the air and hits object 1. • Object 1 will start to vibrate • Tuning fork example
Other resonance examples • • PHET simulation Tacoma Narrows Bridge London Millennium Bridge Breaking a wine glass with your voice
From Resonance to Standing Waves • Using the wave generator, we can create a standing wave. • It looks like the rope is just going up and down… but what is really happening? • The incoming wave, and the reflected wave are interfering causing constructive and destructive interference.
• Areas with no amplitude are nodes. • Areas with amplitude are anti-nodes.
How to get a standing wave • How the standing waves are produced depends on the natural frequencies of the string (or tube for wind instruments). • And natural frequencies depend on… – The size of the object – The material the object is made of – What the object is struck with • Check for understanding… how do you change notes on a guitar or any instrument?
Harmonics • https: //www. youtube. com/watch? v=VRAXK 4 QKJ 1 Q • Check for understanding: Why do different instruments playing the same note sound different?
Resonance Tube • How can we use the following set-up to determine the speed of sound in air?