Among two interfering sources, let `A` be ahead in phase by `54^(@)` relative to `B`. If the observations be taken from point `P`, such that `PB - PA = 1.5 lambda`, deduce the phase difference between the waves from `A` and `B` reaching `P`.

Answer

`3.3 pi radian`

Explanation

Total phase difference `= phi_(1) + phi_(2)`
where `phi_(1) = 54^(@) = 54 xx (pi)/(180) = 0.3 pi radian`,
`phi_(2) = (2pi)/(lambda) xx 1.5 lambda = 3 rad`
`:. phi_(1) + phi_(2) = 0.3 pi + 3 pi = 3.3pi radian`