b) Interference

c) interference, coherence, path difference and phase difference

d) constructive interference and destructive interference in terms of path difference and phase difference

coherence = when two waves have the same frequency and wavelength, and therefore a constant phase difference

stable interference = interference of two coherent waves

maxima = the point on a stable interference pattern where the two waves interfere constructively

minima = the point on a stable interference pattern where the two waves interfere destructively

path difference = difference in distance two waves travel from their sources to when they meet

in phase = when the phase difference is (n) × 360

antiphase = when the phase difference is (n + ½) × 360

for a stable interference pattern

• if the path difference for two waves = integer × λ

  • the two waves will interfere in phase

• if the path difference for two waves = (integer + ½) × λ

  • the two waves will interfere in antiphase