Guitar Strings and Crumbling Bridges

Standing Waves and Resonance

Wave Interference• Waves are “superimposed” like pulses

Example #1

D.Both waves reach maximum

amplitude at that point!

Example #2Draw a new wave based on the

superposition of waves A and B.

A View at the Top

• When viewed from above, a wave source makes circular patterns

crest (wave front)

trough

At this point, twoTROUGHS meet toCONSTRUCTIVELY

interfere

At this point, twoCRESTS meet to

CONSTRUCTIVELYinterfere

At this point, aCRESTS and TROUGH

meet to DESTRUCTIVELYinterfere

Standing Waves• REFLECTION and INTERFERENCE together

result in STANDING WAVES

• Standing waves contain a pattern of NODES and ANTI-NODES

• NODE : stationary points – always 180° out of phase

• ANTI-NODE : maximum displacement – alternate in/out of phase

Example #2

FOUR

Resonance

• Resonance occurs when a medium is vibrated NEAR its NATURAL FREQUENCY

• Constructive interference occurs to an extreme degree causing vibrations with HUGE AMPLITUDE

• If the vibration has enough ENERGY and the correct FREQUENCY, the medium may be damaged or destroyed!

Resonant Systems

SingerSwings