For the visibility of a diffraction pattern of a wave of light,the size of the slit or obstacle should be

$A$ narrow slit of width $2 \, mm$ is illuminated by monochromatic light of wavelength $500 \, nm$. The distance between the first minima on either side on a screen at a distance of $1 \, m$ is ........ $mm$.

Light of wavelength $580 \text{ nm}$ is incident normally on a slit of width '$a$'. The distance between the slit and the screen is $2.5 \text{ m}$ and the distance of the second order maximum from the centre of the screen is $14.5 \text{ mm}$ in a diffraction pattern. The value of '$a$' is

Assertion: The clouds in the sky generally appear to be whitish.
Reason: Diffraction due to clouds is efficient in equal measure at all wavelengths.

Light of wavelength $5000 \, \text{Å}$ is incident on a slit of width $0.1 \, \text{mm}$. Find the width of the central bright fringe on a screen placed at a distance of $2 \, \text{m}$ in $\text{mm}$.

Two slits are $1 \,mm$ apart and the screen is located $1 \,m$ away from the slits. $A$ light of wavelength $500 \,nm$ is used. The width of each slit to obtain $10$ maxima of the double slit pattern within the central maximum of the single slit pattern is $\ldots \ldots \ldots \times 10^{-4} \,m$.