Light of wavelength $600 \,nm$ is incident normally on a slit of width $0.2 \,mm$. The angular width of the central maxima in the diffraction pattern is (measured from minimum to minimum):

Light of wavelength $\lambda$ is incident on a single slit of width $a$ and the distance between the slit and the screen is $D$. In the diffraction pattern, if the slit width is equal to the width of the central maximum, then $D$ is equal to:

Two wavelengths of sodium light $590 \,nm$ and $596 \,nm$ are used one after another to study diffraction due to a single slit of aperture $2 \times 10^{-6} \,m$. The distance between the slit and the screen is $1.5 \,m$. The separation between the positions of the first maximum of the diffraction pattern obtained in the two cases is: (in $\,mm$)

Assertion : When a tiny circular obstacle is placed in the path of light from some distance,a bright spot is seen at the centre of the shadow of the obstacle.
Reason : Destructive interference occurs at the centre of the shadow.

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

When light is incident on a diffraction grating,the zero-order principal maximum will be: