$A$ single slit of width $0.20 \, mm$ is illuminated with light of wavelength $500 \, nm$. The observing screen is placed $80 \, cm$ from the slit. The width of the central bright fringe will be ..... $mm$.

In Fraunhofer diffraction by a single slit,if the slit width is $a$,the wavelength is $\lambda$,and the focal length of the lens is $f$,what is the linear width of the central maximum?

The condition for diffraction is

Two wavelengths $590 \ nm$ and $596 \ nm$ of sodium light are used one after another to study the diffraction taking place at a single slit of aperture $2.4 \ mm$. The distance between the slit and the screen is $2 \ m$. The separation between the positions of the first secondary maximum of the diffraction pattern obtained in the two cases is:

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.

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 ...... $\mathring A$.