Out of given four waves (1),(2),(3) and (4)
`y=asin(kx+omegat)` ..(1)
`y=asin(omegat-kx)` ..(2)
`y=acos(kx+omegat)` ..(3)
`y=acos(omegat-kx)` ..(4)
emitted by four different source `S_1`,`S_2`,`S_3` and `S_4` respectively, interference phenomena would be observed in space under appropriate conditions when

Options

A. Source `S_1` emits wave (1) and `S_2` emits wave (2)
B. Source `S_3` emits wave (3) and `S_4` emits wave (4)
C. Source `S_2` emits wave (2) and `S_4` emits wave (4)
D. `S_4` emits waves (4) and `S_3` emits waves (3)

Answer

C

Explanation

For interference, two waves must have a constant phase relationship Equation `1` and `3` and `2` and `4` have a constant phase relationship of `(pi)/(2)` out of two choices. Only one `S_2` emitting `2` and `S_4` emitting `4` is given so only (c ) option is correct.