Due to which optical phenomenon do we not see the shadow of an opaque object clearly?

Which of the following waves exhibits clear diffraction?

The angular width of the central maxima in the Fraunhofer diffraction pattern of a slit is measured. The slit is illuminated by light of wavelength $6000 \ \mathring A$. When the slit is illuminated by light of another wavelength,the angular width decreases by $30\%$. The wavelength of this light will be ...... $\mathring A$.

$A$ circular disc is placed in front of a narrow source. When the point of observation is at a distance of $1 \, m$ from the disc,the disc covers the first $HPZ$ (Half Period Zone). The intensity at this point is $I_0$. The intensity at a point at a distance of $25 \, cm$ from the disc will be:

Consider sunlight incident on a slit of width $10^4 \ \mathring{A}$. The image seen through the slit shall

In a single slit diffraction experiment,the width of the slit is made double its original width. Then the central maximum of the diffraction pattern will become