When are two vibrating particles said to be in the same phase?
- AIf the phase difference between them is an even multiple of π
- BIf the path difference is an even multiple of (λ/2)
- CIf the time interval is an even multiple of (T/2)
- DAll of the above
Show answer and explanation
Correct answer: (d) All of the above
Explanation
Two particles are in the same phase when their phase difference is 2nπ, that is, an even multiple of π (n = 0, 1, 2 …). The other two conditions mean the same thing:
- path difference: phase difference = (2π/λ) × path difference. A path difference of 2n(λ/2) = nλ gives 2nπ;
- time interval: phase difference = (2π/T) × time interval. A time interval of 2n(T/2) = nT gives 2nπ.
So all three conditions put the particles in the same phase.