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
$\Delta x=\pm \frac{\lambda }{2},\pm \frac{3\lambda }{2},\pm \frac{5\lambda }{2},\pm \frac{7\lambda }{2},\pm \frac{9\lambda }{2}$