When a compact disc $(CD)$ is illuminated by a small source of white light,coloured bands are observed. This is due to

$A$ slit of width $a$ is illuminated by monochromatic light of wavelength $650 \ nm$. The value of the slit width $a$ when the first minimum is formed at a diffraction angle of $30^\circ$ is:

$A$ light wave of wavelength $\lambda$ is incident on a slit of width $d$. The resulting diffraction pattern is observed on a screen at a distance $D$. If the linear width of the principal maxima is equal to the width of the slit,then the distance $D$ is:

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 $\text{mm}$.

$A$ slit of width $d$ is illuminated by light of wavelength $\lambda$. The angular width of the central maximum is:

In the experiment of diffraction at a single slit,if the slit width is decreased,the width of the central maximum