$A$ thin slice is cut out of a glass cylinder along a plane parallel to its axis. The slice is placed on a flat glass plate as shown. The observed interference fringes from this combination shall be

$A$ light of wavelength $5890 \; \mathring{A}$ falls normally on a thin air film. What is the minimum thickness of the film such that the film appears dark in reflected light?

In a biprism experiment, the maximum intensity is $I_0$. If the path difference between the two interfering waves is $\frac{\lambda}{3}$, then the intensity at the point on the screen is [$\sin 30^{\circ} = \cos 60^{\circ} = 0.5, \sin 60^{\circ} = \cos 30^{\circ} = \sqrt{3}/2$].

When a mica sheet of thickness $7 \ \mu m$ and refractive index $\mu = 1.6$ is placed in the path of one of the interfering beams in a biprism experiment, the central fringe shifts to the position of the seventh bright fringe. The wavelength of the light used is $............ \ \mathring{A}$.

In Fresnel's biprism,coherent sources are obtained by ...

In a Fresnel biprism experiment,the two positions of the lens give separations between the virtual slits as $16 \; cm$ and $9 \; cm$ respectively. What is the actual distance of separation (in $cm$)?