$A$ very thin transparent film (like a soap bubble) is viewed in white light. The color of the film appears .......

$A$ mixture of yellow light of wavelength $580 \ nm$ and blue light of wavelength $450 \ nm$ is incident normally on an air film of thickness $2.9 \times 10^{-4} \ mm$. The colour of reflected light is

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 $............ \ \mathring{A}$.

$A$ transparent film of refractive index $2.0$ is coated on a glass slab of refractive index $1.45$. What is the minimum thickness of the transparent film to be coated for the maximum transmission of green light of wavelength $550 \ \text{nm}$ (in $\text{nm}$)? [Assume that the light is incident nearly perpendicular to the glass surface.]

$A$ 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

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.