Coherent – waves emitted in the same phase from multiple sources
An interference pattern is observed when two sources of wave of the same wavelength, frequency and amplitude are coherent and are emitted close to each other.
This can also be done with a single wave source being passed through two nearby gaps/slits and diffracted
Both sources of wave must be of the same type (longitudinal/transverse)
Waves must meet at same time
Waves must have the same polarisation
Sources must be coherent – the frequency, wavelength, speed and amplitude of the wave must therefore also be the same
