In a Young’s double slit experiment the spacing between the slits is 0.3 mm and the screen is kept at a distance of 1.5 m. The second bright fringe is found to be displaced by 6 mm from the central fringe. The wavelength of the light used in the experiment is :-

A beam of light of $\lambda =600 \mathrm{nm}$ from a distant source falls on a single slit $1 \mathrm{mm}$ wide and the resulting diffraction pattern is observed on a screen $2 \mathrm{m}$ away. The distance between the first dark fringes on either side of the central bright fringe is

In a double slit experiment, the two slits are $1 \mathrm{mm}$ apart and the screen is placed $1 \mathrm{m}$ away. A monochromatic light of wavelength $500 \mathrm{nm}$ is used. What will be the width of each slit for obtaining ten maxima of double slit within the central maxima of single slit pattern? 

For a parallel beam of monochromatic light of wavelength $\lambda$ diffraction is produced by a single slit whose width $a$ is of the order of the wavelength of the light. If $D$ is the distance of the screen from the slit, the width of the central maxima will be