Question

$S_1,S_2$ are two coherent sources (having initial phase difference zero) of sound located along $x$ −axis separated by $4\lambda$ where $\lambda$ is wavelength of sound emitted by them. Number of maxima located on the elliptical boundary around it will be : [ $S_1$ and $S_2$ are assumed to be at focus of ellipse]

• A. 16
• B. 12
• C. 8
• D. 4

Answer 1

Answer: (A)

$S_{1}P-S_{2}P=0$
$S_{1}Q-S_{2}Q=4\lambda$
$\therefore$ 3 maximum lie on are between P and Q. Counting all quadrants; the total number is 12. P and Q symmetrical points are also maxima.
$\therefore$ Total number is 16