Light of wavelength $600 \, nm$ is incident on a double slit and the interference fringes are formed on a screen $1 \, m$ apart. The separation between two consecutive dark fringes on a screen is found to be $1.2 \, mm$. What is the separation between the slits in $mm$?

In $YDSE$ with two identical slits,when the upper slit is covered with a transparent sheet of mica,the second-order minima is observed above the center of the screen and the second-order maxima below it. Which of the following cannot be a possible value of the phase difference caused by the mica sheet?

In a Young's double-slit experiment,the wavelength of light used is $6000 \, \mathring A$. The phase difference between the central bright fringe and the third bright fringe is .......

In an interference pattern,the $(n + 4)^{th}$ order blue bright fringe and the $n^{th}$ order red bright fringe coincide at a point. If the wavelengths of red and blue light are $7800 \, \mathring{A}$ and $5200 \, \mathring{A}$ respectively,then the value of $n$ is . . . . . .

The fringe width for red colour as compared to that for violet colour is approximately (in $\times$)

In $Y.D.S.E$,the ratio of intensity of maxima and minima is $25 : 9$. The ratio of slit width is