The angular width of the central maxima in Fraunhofer diffraction for $\lambda = 6000 \; \mathring{A}$ is $\theta_{0}$. When the same slit is illuminated by another monochromatic light,the angular width decreases by $30 \%$. The wavelength of this light is ....... $\mathring{A}$.

Estimate the distance for which ray optics is a good approximation for an aperture of $4 \; mm$ and wavelength $400 \; nm$.

In Fresnel diffraction,if the distance between the disc and the screen is decreased,the intensity of the central bright spot will

For what distance is ray optics a good approximation when the aperture is $ 4 \,mm $ and the wavelength of light is $ 400 \,nm $ (in $\,m$)?

The condition for observing Fraunhofer diffraction from a single slit is that the wave front incident on the slit should be ............

Consider the following statements $A$ and $B$ and identify the correct answer:
$A$. Fresnel's diffraction pattern occurs when the source of light or the screen on which the diffraction pattern is seen,or when both are at a finite distance from the aperture.
$B$. Diffracted light can be used to estimate the helical structure of nucleic acids.