An important feature of waves is that since they are disturbance in a medium that carry energy, when two waves overlap in the same place in the medium, they add up. This is the idea of superposition.
Interactive
Before we examine the theory, you will get an idea of superposition by playing with an interactive.
Examine the animation below. (courtesy Tom Walsh)
Interactive
Before we examine the theory, you will get an idea of superposition by playing with an interactive.
Examine the animation below. (courtesy Tom Walsh)
- Start by setting the pulse heigh and pulse width for both wave fully to the right, and press play. What do you notice?
If you click the checkbox, to reveal individual pulses, you can see what happens. - Now place one pulse height to the left. It should now be the reverse of the other pulse. Again play and observe.
What you will find that the waves add up whilst the overlap, that is, their individual amplitudes determine the resultant amplitude at that moment in space and time.
This can result in a resultant larger amplitude - if both pulse are above the equilibrium line, or smaller, or even cancel out - if one is below the equilibrium line. This adding or 'overlapping' is called superposition.
The result is an "interference" of the wave by another wave - hence it is also called interference.
When the waves 'add', it is called constructive interference, and when they 'subtract', it is called destructive interference.
This can result in a resultant larger amplitude - if both pulse are above the equilibrium line, or smaller, or even cancel out - if one is below the equilibrium line. This adding or 'overlapping' is called superposition.
The result is an "interference" of the wave by another wave - hence it is also called interference.
When the waves 'add', it is called constructive interference, and when they 'subtract', it is called destructive interference.
Video
Let's now examine this more closely with this video which looks at what superposition is and how it relates to interference from a 1D perspective.
Let's now examine this more closely with this video which looks at what superposition is and how it relates to interference from a 1D perspective.
Superposition , or the adding of waves, can be demonstrated and explained by using Desmos, a powerful online graphing calculator.
Start first by watching this video which explains the principles on how to use Desmos as well as the basics of understanding the wave equation. Then, using Desmos you can show superposition in real time, ie as a function of time. Now use this Desmos activity that shows wave addition
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