[单选题]
A coherent light is incident on a double slit that
lz-d*(g)sn e ilf66xz 1*aalx has slit separation of
k: ly0/p m z;byi74:b*shhajy $d$ and slit width of $b$. An interference pattern on a screen is observed. The graph shows the variation of intensity with distance from the centre of the pattern.
$S_1$, $S_2$ and $S_3$ are the separations between various points on the pattern and the center of the pattern. The distance between the screen and slits is $D$. What is the wavelength of the incident light?