Waves -Diffraction and two source interference

Interference

When two or more waves pass through each other, the displacement of the medium caused by each individual wave combine to create a resultant wave

Diffraction

Bending of waves around obstacles. Maximum diffraction occurs when obstacle is similar size to wavelength

monochromatic

sources have a single frequency (‘one colour’)

coherent

Each source is ‘in-time’ or ‘in-phase’ this means when one source is sending a crest so is the other source

Constructive interference

occurs when path difference=nlambda (n=0,1,2,3,…)

Destructive interference

occurs when path difference=(n+1/2)lambda (n=0,1,2,3,…)

Diffraction grating

Series of fine slits or lines used to deviate waves e.g. light