The colors seen on an oil film floating on the surface of water are due to interference. What should be the order of the thickness of the oil film?

$A$ 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

$A$ parallel coherent beam of light falls on a Fresnel biprism of refractive index $\mu$ and refracting angle $\alpha$. The fringe width on a screen at a distance $D$ from the biprism will be (wavelength $= \lambda$).

$A$ 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?

Choose the correct statement.

In a biprism experiment,monochromatic light of wavelength $\lambda$ is used. The distance between the two coherent sources $d$ is kept constant. If the distance between the slit and the eyepiece $D$ is varied as $D_1, D_2, D_3, D_4$ and the corresponding measured fringe widths are $W_1, W_2, W_3, W_4$,then: