In Young's double slit experiment, in an interference pattern, second minimum is observed exactly in front of one slit. The distance between the two coherent sources is ' $d$ ' and the distance between the source and screen is ' $D$ '. The wave length of light $(\lambda)$ used is

A screen is placed at 50 cm from a single slit, which is illuminated with light of wavelength 600 nm . If separation between the $1^{\text {st }}$ and $3^{\text {rd }}$ minima in the diffraction pattern is 3 mm then slit width is

In Young's double slit experiment using monochromatic light of wavelength ' $\lambda$ ', the intensity of light at a point on the screen where path difference ' $\lambda$ ' is K units. The intensity of light at a point where the path difference is $\frac{\lambda}{6}$ is $\left[\cos \frac{\pi}{6}=\sin \frac{\pi}{3}=\frac{\sqrt{3}}{2}\right]$

In an interference experiment, the $\mathrm{n}^{\text {th }}$ bright fringe for light of wavelength $\lambda_1(\mathrm{n}=0,1,2,3 \ldots)$ coincides with the $\mathrm{m}^{\text {th }}$ dark fringe for light of wavelength $\lambda_2(\mathrm{~m}=1,2,3 \ldots)$. The ratio $\frac{\lambda_1}{\lambda_2}$ is