Slide 1 - Warm Up

• Go to
• http://www.theuniverseandmore.com/
• Click Wave applet
• Use the applet to decide who is correct.

Slide 2 - Interference

Slide 3

• interference is when two waves combine to form a resultant wave of greater or lower amplitude.

Slide 4 - Constructive interference

• When two waves meet, they interfere with each other.
• If they meet each other exactly in phase, the amplitudes ‘add up’ to produce large crests and troughs.
• +
• =
• This is called constructive interference.

Slide 5 - CONSTRUCTIVE INTERFERENCE

• larger displacement (larger amplitude)
• crest overlaps crest 
• or trough overlaps trough

Slide 6 - Destructive interference

• This is called destructive interference.
• If two waves meet each other exactly out of phase, the amplitudes ‘subtract’ to produce no peaks or crests.
• +
• =

Slide 7 - DESTRUCTIVE INTERFERENCE

• smaller displacement (smaller amplitude)
• crest cancels trough 
• crest overlaps trough 
• displacement/ amplitude is reduced

Slide 8 - This is how noise canceling headphones work!