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# In Physics, What Is Interference?

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• Written By: Alex Paul
• Edited By: Angela B.
2003-2018
Conjecture Corporation
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Interference, in physics, can refer to two phenomena. The most common is wave interference. This happens when two or more waves meet in the same place, resulting in the waves either combining or cancelling each other out. When coherent waves with similar frequencies meet, the result can be a consistent interference pattern. The other phenomenon is communication interference, which is when a radio wave signal becomes distorted.

There are many different types of waves. Electromagnetic waves are made of oscillating electric and magnetic fields and move at the speed of light. Visible light, X-rays, microwaves and ultraviolet (UV) light are all examples of electromagnetic waves. Sound also is a wave, although it travels differently than light and can’t move in a vacuum.

When two waves collide, the effect is something known as wave interference. This means the waves will pass through each other but, while in the same location, interact with one another. The result is a change in amplitude, or size, of the two waves.

There are two types of wave interference, known as constructive and destructive. If two waves meet at their greatest point, then the two waves add together; this is known as constructive. It creates a wave that’s double the size while the crests of the waves are overlapping. The same happens if the two waves meet each other at their lowest points.

Destructive interaction happens when two waves meet each other at opposite points of oscillation. If, for example, one wave is at its positive peak and another at its negative peak, then the waves cancel each other out. For waves with exactly the same amplitude, the result is no wave at the point of collision.

All waves passing through each other show wave interference, but this is random if the waves come from different sources with different frequencies. Interference can be used for practical purposes if two waves are coherent, which means they have very similar frequencies. This is because two waves of the same frequency will consistently meet each other in the same point of oscillation. For example, if the waves meet at a point where they are exactly in sync, then the resulting wave will have double the amplitude.

In communication, interference has a different meaning. Radio wave communication experts use the term to refer to anything that causes distortion in the wave. Other electromagnetic waves, for example, can often cause distortion.