Which of the following waves exhibits clear diffraction?

Angular width $(\beta)$ of the central maximum of a diffraction pattern on a single slit does not depend upon

The diffraction effect can be observed in

$A$ slit of width $a$ is illuminated by red light of wavelength $6500 \, \mathring{A}$. The first minimum will fall at $\theta = 30^{\circ}$ if $a$ is equal to:

In a single slit diffraction pattern,the distance between the plane of the slit and the screen is $1.3 \ m$. The width of the slit is $0.65 \ mm$ and the second maximum is formed at a distance of $2.6 \ mm$ from the center of the screen. The wavelength of light used is: (in $Å$)

In a Fraunhofer's diffraction obtained by a single slit aperture,the value of path difference for $n^{th}$ order of minima is