Figure shows equidistant slits being illuminated by a monochromatic parallel beam of light.

Figure shows equidistant slits being illuminated by a monochromatic parallel beam of light. Let

$B P_{0}-A P_{0}=\lambda / 3$ and $\mathrm{D}>\lambda$

(a) Show that in this case $=\sqrt{2 \lambda D / 3}$

(b) Show that the intensity at $P_{0}$ slits individually.