the particles of a medium vibrate about thier mean positions whenever a wave travels through that medium. the phase difference between the vibrations of two such particles.
a)varies with time
b)varies with distance separating them
c)varies with time as well as distance
d)is always zero
The answer is b as the wave pass through the medium the oscillation frequency does not change but the displacement of the particle changed due to movement in the medium. therefore the phase will vary as distance varies .