A student describes two light waves as being coherent. What does this tell you about the waves?
They have a constant phase difference and the same frequency.
They travel at different speeds in the same medium.
They are polarized in perpendicular planes.
They have a range of different wavelengths.
237 exam-style questions on CIE IGCSE Physics General properties of waves, covering General properties of waves. Each one has a worked solution and a mark scheme showing where the marks go.