Thin film interference happens with________.

Thin interference film happens with

In a biprism experiment, the distance between the $3^{\text {rd }}$ and $12^{\text {th }}$ bright bands when light of wavelength $6000 \mathrm{\AA }$ is used is the same as the distance between $4^{\text {th }}$ and $14^{\text {th }}$ bright bands of light of wavelength $\lambda$. The value of $\lambda$ is

In the YDSE shown the two slits are covered with thin sheets having thickness $t \text{\&} 2t$ and refractive index $2\mu$ and $\mu .$ Find the position $\left(y\right)$ of central maxima

Direction: The question has a paragraph followed by two statements, Statement$-1$ and statement$-2$. Of the given four alternatives after the statements, choose the one that describes the statements. A thin air film is formed by putting the convex surface of a plane-convex lens over a plane glass plate. With monochromatic light, this film gives an interference pattern due to light reflected from the top (convex) surface and the bottom (glass plate) surface of the film.

$\mathrm{Statement}-1:$ When light reflects from the air-glass plate interface, the reflected wave suffers a phase change of $\mathrm{\pi }$.

$\mathrm{Statement}-2:$ The centre of the interference pattern is dark.