In a double-slit experiment,the distance between the slits is $d$. The screen is at a distance $D$ from the slits. If a bright fringe is formed opposite to one of the slits,its order $n$ is:

Two sources of light of wavelengths $2500 \text{ Å}$ and $3500 \text{ Å}$ are used in Young's double slit experiment simultaneously. Which orders of fringes of the two wavelength patterns coincide?

The fringe width in a $YDSE$ pattern is $2.4 \times 10^{-4} \, m$ when red light of wavelength $6400 \, \mathring{A}$ is used. How much will it change if blue light of wavelength $4000 \, \mathring{A}$ is used?

In $YDSE$,let $S_1$ and $S_2$ be the two slits,and $C$ be the centre of the screen. If $\angle S_1 C S_2 = \theta$ and $\lambda$ is the wavelength,the fringe width is

$A$ mixture of light,consisting of wavelengths $590 \ nm$ and an unknown wavelength,illuminates Young's double slit and gives rise to two overlapping interference patterns on the screen. The central maximum of both lights coincide. Further,it is observed that the $3^{rd}$ bright fringe of the known light coincides with the $4^{th}$ bright fringe of the unknown light. From this data,the wavelength of the unknown light is ...... $nm$.

In a Young's double slit experiment,the wavelength of red light is $7.8 \times 10^{-5} \,cm$ and that of blue light is $5.2 \times 10^{-5} \,cm$. The value of $n$ for which $(n+1)^{\text{th}}$ blue bright band coincides with $n^{\text{th}}$ bright red band is ..........