Question

Two point monochromatic and coherent sources of light of wavelength A are each placed as shown in the figure below. The initial phase difference between the sources is zero. Select the incorrect statement.

• A. If $d =\frac{7\lambda}{2},O$ will be minima
• B. If $d = \lambda$, only one maxima can be observed on screen
• C. If $d = 4.8 \lambda$, then total $10$ minimas would be there on screen
• D. If $d =\frac{5\lambda}{2}$, then intensity at $O$ would be maximum.

Answer 1

Answer: (D)

Path difference, $\Delta x$ at $O =d$,
So, if $d= \frac{7\lambda}{2}, O $will be a minima.
If $d = \lambda, O$ will be maxima.
If $ d= \frac{5\lambda}{2}, O$ will be minima and hence intensity is minimum.
If $d = 4.8 \,\lambda$, then total $10$ minimas can be observed on screen, $5$ above and $5$ below $O$, which correspond to
$\Delta x = \pm\frac{\lambda}{2}, \pm\frac{3\lambda}{2}, \pm \frac{5\lambda}{2}, \pm \frac{7\lambda}{2}, \pm\frac{9\lambda}{2}$