Question

# Figure here shows *P* and *Q* as two equally intense coherent sources emitting radiations of wavelength 20 *m*. The separation *PQ* is 5.0 *m* and phase of *P* is ahead of the phase of *Q* by . *A*, *B* and *C* are three distant points of observation equidistant from the mid-point of *P**Q.* The intensity of radiations at *A*, *B*, *C* will bear the ratio

- 0 : 1 : 4
- 4 : 1 : 0
- 0 : 1 : 2
- 2 : 1 : 0

## The correct answer is: 2 : 1 : 0

### Since *P* is ahead of *Q* by and path difference between *P* and *Q* is Therefore at *A*, phase difference is zero, so intensity is 4*I*. At *C* it is zero and at *B*, the phase difference is , so intensity is 2*I*.

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