In a Fresnel's biprism experiment,the distance between the source and the screen is $1 \, m$ and the distance between the source and the biprism is $10 \, cm$. The wavelength of light is $6000 \, \mathring{A}$. The fringe width is $0.03 \, cm$ and the refracting angle of the biprism is $1^\circ$. Find the refractive index of the material of the biprism.

$A$ thin transparent film with refractive index $1.4$ is held on a circular ring of radius $1.8 \ cm$. The fluid in the film evaporates such that transmission through the film at wavelength $560 \ nm$ goes to a minimum every $12 \ seconds$. Assuming that the film is flat on its two sides, the rate of evaporation is . . . . . . $\pi \times 10^{-13} \ m^3/s$.

$A$ parallel beam of light of intensity $I_0$ is incident on a glass plate. $25 \%$ of light is reflected by the upper surface and $50 \%$ of light is reflected from the lower surface. The ratio of maximum to minimum intensity in the interference region of the reflected rays is

To ensure almost $100$ per cent transmittivity,photographic lenses are often coated with a thin layer of dielectric material. The refractive index of this material is intermediate between that of air and glass (which makes the optical element of the lens). $A$ typically used dielectric film is $MgF_2$ $(n = 1.38)$. What should the thickness of the film be so that at the center of the visible spectrum $5500 \, \mathring{A}$ there is maximum transmission?

In a Fresnel's biprism experiment,the fringe width is $1 \,mm$. The distance of the nearest dark fringe from the central bright fringe is .......$mm$.

If Fresnel's biprism experiment is performed in water instead of air,what will be the effect on the fringe width?