The luminous border that surrounds the profile of a mountain just before the sun rises behind it is an example of:

Write the thoughts expressed by Richard Feynman regarding the difference between interference and diffraction.

If the measured angular separation between the second minimum to the left of the central maximum and the third minimum to the right of the central maximum is $30^{\circ}$ in a single slit diffraction pattern recorded using $628 \ nm$ light,then the width of the slit is . . . . . . $\mu m$.

$A$ circular disc is placed in front of a narrow source. When the point of observation is $2 \, m$ from the disc,it covers the first $HPZ$. The intensity at this point is $I$. When the point of observation is $25 \, cm$ from the disc,the intensity will be:

The radius $r$ of the $n^{th}$ half-period zone is proportional to:

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