what is constractive interfearence?

When two waves interfere and gives the resultant wave which has amplitude greater than the individual waves amplitude is called constructive interference.

 Constructive interference is a type of interference that occurs at any location along the medium where the two interfering waves have a displacement in the same direction. In this case, both waves have an upward displacement; consequently, the medium has an upward displacement that is greater than the displacement of the two interfering pulses. Constructive interference is observed at any location where the two interfering waves are displaced upward. But it is also observed when both interfering waves are displaced downward.

The path difference between two waves is zero, and it is integral multiple of wavelength is called constructive interfearence.

In constructive interfearence amplitude willbe high due to waves are in phase then we got bright.