To observe diffraction,the size of an obstacle:

Assertion : Standard optical diffraction gratings cannot be used for discriminating between $X-$ray wavelengths.
Reason : The grating spacing is not of the order of $X-$ray wavelengths.

$A$ Fraunhofer diffraction pattern due to a single slit of width $0.3 \text{ mm}$ is obtained on a screen placed at a distance of $3 \text{ m}$ from the slit. The first minima lie at $5.5 \text{ mm}$ on either side of the central maximum on the screen. The wavelength of light used is (in $\text{ Å}$)

$A$ 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 condition for obtaining secondary maxima in the diffraction pattern due to a single slit is:

In a diffraction experiment from a single slit,the angular width of the central maximum does $NOT$ depend upon: