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

$A$ single slit diffraction pattern is formed with white light. For what wavelength of light, the $3^{\text{rd}}$ secondary maximum in the diffraction pattern coincides with the $2^{\text{nd}}$ secondary maximum in the pattern of red light of wavelength $6000 \text{ Å}$ (in $\text{ Å}$)?

The diffraction effect can be observed in

$A$ diffraction pattern is obtained by using a beam of red light. What will happen if the red light is replaced by blue light?

Light of wavelength $589.3 \, nm$ is incident normally on a slit of width $0.1 \, mm$. What will be the angular width of the central diffraction maximum in degrees?