Fact of the Day: 11/10/2021

In physics, the term “interference” refers to wave behavior, when two waves have coinciding paths. If the two waves have the same frequency and phase (and, therefore, the same period), then the waves will reinforce each other when they’re added, producing a resultant wave with an amplitude greater than either of the individual waves. This phenomenon is called constructive interference. In perfect constructive interference, when the waves are exactly in phase, the amplitude of the resultant wave will be exactly equal to the sum of the original individual wave amplitudes.

If two waves are out of phase exactly so that the minimum of one wave occurs at the maximum of the other wave (they’re out of phase by ½ of the period), then the waves will cancel each other out in destructive interference, provided they have the same amplitude. If the two waves do not have the same amplitude, the resultant wave will have an amplitude that is the difference of the larger amplitude and the smaller one.

Different combinations of waves will undergo different forms of interference, producing interesting shapes. 

If you’d like to explore this, open up a graphing calculator (like www.desmos.com/calculator) and type in equations adding sine and cosine waves—for example, y = sin(x) + cos(x). To see this as a resultant wave, you can type in y = sin(x) and y = cos(x) separately as well. You’ll notice that the amplitude of the first curve (the sum of the two waves) is greater than that of either of the individual waves. Play around with the amplitudes of the sine and cosine functions, and try changing their periods, too. These functions model various types of interference that occur when waves, such as sound waves, vibrate at the same time.

Reference(s): https://www.britannica.com/science/interference-physics#ref135703 

Fact Author: Ace 

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