Question

$S_1$ and $S_2$ are the two coherent point sources of light located in the $xy-plane$ at points $(0,0)$ and $(0,3λ)$ respectively. Here $\lambda$ is the wavelength of light. At which one of the following points (given as coordinates), the intensity of interference will be maximum?

• A. $(3\lambda, 0)$
• B. $(4\lambda, 0)$
• C. $(5\lambda/4, 0)$
• D. $(2\lambda/3, 0)$

Answer 1

Answer: (B)

The given situation can be show as

The intensity will be maximum at those given points where the path difference between the two interfering waves is an integral multiple of wavelength i.e., $\Delta x=n \lambda$
For the the given points, the intensity will be maximum for $(4 \lambda, 0)$.