When two or more waves of same wavelength and frequency join each other to form a single wave, interference occurs. There are two types of interference depending on how the waves collided these are Constructive interference and Destructive interference.
Constructive Interference: Lets say that two waves of same frequency and wavelength collide. They collide in such a way that crest of first wave collides with the crest of second wave and similarly the trough of first wave collides with the trough of second wave. In this case the crest and troughs of both waves will add up to form a wave having amplitude equal to the sum of both the waves. This type of interference is called Constructive interference.
Destructive Interference: Now lets say that both waves collided in such way that crest of first wave collides with the trough of second wave and trough of first wave collides with the crest of second wave. In this case the crest and trough of both waves will cancel each other to form a wave that will have amplitude equal to the difference of the amplitudes of both the waves. If initially the amplitude of both the waves was same then after this interference the amplitude will become zero. This type of interference is called Destructive Interference.
This phenomenon is based upon the principle of superposition of waves, according to which, when a number of wave disturbances pass through a given point in a medium, the resultant disturbance produced at that point, is the vector sum of the disturbances due to the individual waves.
If there is an increase in the intensity of light, it is called constructive interference.
If there is a decrease in the intensity of light, it is called destructive interference.
Constructive Interference : - In which the magnitude of resultant wave increases.
Destructive Interference : - In which the magnitude of resultant wave decreases.
Principle of superposition
The principle of superposition of waves states that when two or more propagating waves of same type are incident on the same point, the resultant amplitude at that point is equal to the vector sum of the amplitudes of the individual waves.
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