Page 9 - Topic 3

CONSTRUCTIVE AND DESTRUCTIVE INTERFERENCE

This should be a refresher but…. Here’s a website to help. https://ophysics.com/w2.html

Constructive interference

If two identical waves at a point are in phase, then the principle of superposition states that the
resultant amplitude will be the vector sum of the individual amplitudes. i.e double the
amplitude of the individual waves.

Destructive interference

If two identical waves at a point are out of phase, then the principle of superposition states that the resultant
amplitude will be the vector sum of the individual amplitudes. i.e the resultant waves amplitude will be zero.

TWO SOURCE INTERFERENCE

https://phet.colorado.edu/en/simulation/wave-interference

If two coherent sources interfere with each other they will

• Constructively interfere when the path difference from the sources to the point is
1
• Destructively interfere when the path difference from the source to the point is � + �
2
Where ∈ ℤ.