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# Destructive Interference

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Last updated date: 02nd Aug 2024
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## Destructive Interference and Constructive Interference

Before knowing about the destructive interference, a few basic things are to be known. These inferences start from “What is wave?”, “What is interference and its type?”, “Where this destructive interference comes under this?”

Waves

Waves are found everywhere in our daily life. Sound waves, visible light waves, radio waves, microwaves, sine waves, cosine waves, stadium waves, earthquake waves, waves on a string and so on are some of the examples of waves.

The repeating and periodic disturbances that are practiced through a medium from one end of the location to another is referred to as a wave. The wave is a transverse wave if the wave is moving perpendicular to a medium, in which the particles of the medium are displaced in a direction perpendicular to the direction of energy transport.

What is a Medium?

A medium is a substance or material by which the wave is carried; also called wave medium. In general, a wave transports energy and not matter. The particles of the medium get temporarily displaced from its rest position. The force acting upon the particles will restore them to their original positions. So, waves are said to be transporters of energy. The disturbance in the position of one particle will pass to its nearby particles in a repeated and periodic way. Thus the energy is transported from one end to the other.

Anatomy of Wave:

Wave has the crest and trough. The crest is the point on the medium that exhibits the maximum amount of positive or upward displacement from the zero position or rest position. The trough is the point on the medium that exhibits the maximum amount of negative or downward displacement from the zero position or rest position.

A wave has many crests that are often followed by other crests; same happens in the case of trough. Every crest is broken by a trough to create an alternating pattern of crests and troughs.

Properties of wave

Amplitude
: The amplitude of a wave refers to the maximum amount of displacement of a particle from its rest position.

Wavelength: The wavelength of a wave is simply the length of one complete wave cycle, comprising a crest and a trough.

Interference of Waves

When two waves travel through the same medium and meet one another, depending upon the medium their effects may vary. Explaining this is the explanation of interference of waves.

What is Interference?

When two waves meet while traveling along the same medium where interference occurs, this phenomenon is called wave interference. The interference of waves forms particle in the medium to take a shape and that results from the net effect of the two individual waves. To begin the exploration of wave interference, consider two waves of the same amplitudes are traveling in different directions in the same medium. Consider that each wave displaces an upward 1 unit at its crest and has the shape of a sine wave. As the sine pulses move towards each other, eventually there will be a moment in time when they will be completely overlapped. At that time, the obtained wave shape would be an upward displaced sine pulse with amplitude of 2 units. The figures below depicts the before and during interference snapshots of the medium for two such wave pulses. The individual sine pulses are drawn in red and blue colour, and the resulting displacement of the medium is drawn in green colour.

You know depending upon the direction of the waves’ displacement or any two waves’ displacement direction, their interference is identified as constructive interference and destructive interference.

Constructive Interference

This interference occurs at any location along the medium where the two interfering waves have a displacement in the same direction. Here an upward displacement is greater than the displacement of the two interfering pulses. Simply, a constructive interference is observed at any location along a medium where the two interfering waves are displaced upward. It is also observed when both interfering waves are displaced not only upward, but also downward. This is shown in the figure below for two downward displaced pulses.

Here a sine pulse with a maximum displacement of –1 unit, negative sign explains that the displacement is downward. Again, the interference is with a sine pulse with a maximum displacement of –1 unit. These two pulses are shown in red and blue colour. The resulting shape of the medium is a sine wave with a maximum displacement of –2 units.

Destructive Interference

Destructive interference can take place at any location in the medium where the two interfering waves have a displacement in the opposite direction; that the two waves are travelling in an opposite direction when they get into interference. For instance, when a sine pulse with a maximum displacement of +1 unit meets a sine pulse with a maximum displacement of –1 unit, a destructive interference takes place. This is shown in the figure below.