(WVS) Interference Lesson

Interference

When raindrops fall into still water, they create tiny waves that spread out in all directions away from the drops. What happens when the waves from two different raindrops meet? They interfere with each other.

Wave interference occurs when two or more waves pass through the same medium at the same time in the same place. When they do they interact with each other to form a different disturbance at that point.    

Constructive interference takes place when two waves meet each other to create a larger wave. The amplitude of the resulting wave is the sum of the amplitudes of the two initial waves. This could be two crests meeting or two troughs meeting.  

Destructive interference takes place when two waves meet and result in a smaller amplitude disturbance. The amplitude of the resulting wave is the sum of the amplitudes of the two initial waves, but the one amplitude will be a negative number.

Destructive Interference description

Learn about resonance in this video below adapted from the Encyclopedia of Physics Demonstrations.  A demonstrator taps a glass beaker to find its natural frequency of vibration and then sets an oscilloscope and amplifier to produce a loud sound at that same frequency. The resonance created by exposing the beaker to the sound wave forces the glass to vibrate and distorts the shape of the beaker. The amplitude of the sound wave from the speaker is increased until the oscillation of the beaker exceeds the elastic limit of the glass and the beaker breaks.

 

[CC BY 4.0] UNLESS OTHERWISE NOTED | IMAGES: LICENSED AND USED ACCORDING TO TERMS OF SUBSCRIPTION