Which scientist discovered the phenomenon of diffraction of light?

If $\lambda = 6000 \, \mathring{A}$ and $a = 18 \times 10^{-5} \, \text{cm}$,find the angular width of the central maximum in degrees $(^\circ)$.

$A$ parallel beam of light of wavelength $\lambda$ is incident normally on a single slit of width $d$. Diffraction bands are obtained on a screen placed at a distance $D$ from the slit. The second dark band from the central bright band will be at a distance given by

$A$ parallel beam of monochromatic light of wavelength $600 \,nm$ passes through a single slit of $0.4 \,mm$ width. The angular divergence corresponding to the second-order minima would be $...... \times 10^{-3} \,rad$.

In order to see diffraction,the thickness of the film must be of the order of:

Red light is generally used to observe a diffraction pattern. If green light is used instead of red light,the diffraction pattern will.....