In a Young's double-slit experiment using unequal slit widths, the intensity at a point midway between a bright and dark fringes is $4I.$ If one slit is covered by an opaque film, intensity at that point becomes $2I.$ If the other is covered instead, the intensity at that point is

Two ideal slits ${\mathrm{S}}_1$ and ${\mathrm{S}}_2$ are at a distance $d$ apart and illuminated by light of wavelength $\lambda$ passing through an ideal source slit $\mathrm{S}$ placed on the line through ${\mathrm{S}}_2$ as shown. The distance between the planes of slits and the source slit is $D$.

A screen is held at a distance $D$ from the plane of the slits. The minimum value of $d$ for which there is darkness at $\mathrm{O}$ is

A beam of light parallel to central line $\mathrm{AB}$ is incident on the plane of slits. The number of minima obtained on the large screen is $n_1$. Now, if the beam is tilted by some angle $\left(\ne 90°\right)$ as shown in the figure, then the number of minima obtained is $n_2$. Then