Question $8$: In Young's double$-$slit experiment, the distance between the slits is kept about the size of the wavelength of the light, $.$ Why? Justify your statement$($s$)$ using mathematical expressions and physical analyses.

Question $9$: Two slits separated by $0\mathrm{.}250mm$ produce an interference pattern in which the fifth dark fringe is located a $12\mathrm{.}8cm$ above the center of the screen. Determine the distance between the screen and the double$-$slit.

Question $10$: What are the three $(3)$ criteria of a monochromatic light?

Question $1$: If the different Young's double$-$slit experiment have the slit separation ratio of $5$:$1,$ obtain the ratio of the intensity of maxima and minima in the interference pattern.

Question $2$: In Young's double$-$slit experiment, the wavelength of the monochromatic light is $.$ The intensity of light at point $P$ on the screen when the path difference is $5$ is given by $I_0.$ What is the intensity when the path difference is $10?$

Question $3$: Two sources of light waves, $S_1$ and $S_2,$ having the different intensity interfere at point $P.$ The ratio of the maximum intensity to the minimum intensity formed on the screen is $9$:$1.$ What is the ratio of the intensities of light originated from $S_1$ and $S_2?$

Question $4$: Show that the intensity of light produced by the double$-$slit experiment is given by$,$

$I=I_{0}cos(\frac{yd}{L})$

where $y$ is the position on the screen, $d$ is the slits separation, and $L$ is the distance between the two slits.