In $YDSE$ experiment,the $4^{\text{th}}$ dark band is formed opposite to one of the slits. The wavelength of light used is ($d=$ distance between the slits,$D=$ distance between source and the screen)

In Young's experiment,obtain the distance between two consecutive bright fringes and two consecutive dark fringes.

$A$ beam of light consisting of wavelengths $650 \ nm$ and $550 \ nm$ illuminates the Young's double slits with separation of $2 \ mm$ such that the interference fringes are formed on a screen, placed at a distance of $1.2 \ m$ from the slits. The least distance of a point from the central maximum, where the bright fringes due to both the wavelengths coincide, is . . . . . . $\times 10^{-5} \ m$.

In Young's double-slit experiment,a thin mica sheet of thickness $12 \times 10^{-7} \ m$ is placed in the path of one of the interfering beams. It is observed that the central bright fringe shifts by a distance equal to the fringe width. If the wavelength of light used is $6 \times 10^{-7} \ m$,find the refractive index of the mica sheet.

Which of the following is true in $YDSE$?

$A$ laser light of wavelength $630 \, nm$ is incident on a pair of slits,and the fringe width of the interference pattern produced is $8.1 \, mm$. In another interference pattern produced by a different light,the fringe width is $7.2 \, mm$. Find the wavelength of this second light in $nm$.