In Fraunhofer diffraction pattern,slit width is $0.3 \ mm$ and screen is at $1.5 \ m$ away from the lens. If wavelength of light used is $4500 \ Å$,then the distance between the first minimum on either side of the central maximum is [ $\theta$ is small and measured in radian.] (in $mm$)

In a Fresnel diffraction arrangement,the screen is at a distance of $2 \ m$ from a circular aperture. It is found that for light of wavelengths ${\lambda _1}$ and ${\lambda _2},$ the radius of the $4^{th}$ zone for ${\lambda _1}$ coincides with the radius of the $5^{th}$ zone for ${\lambda _2}.$ Then the ratio ${\lambda _1}:{\lambda _2}$ is

What is Fresnel distance? Write its formula.

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.

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

$A$ light beam of wavelength $800 \,nm$ passes through a single slit and is projected on a screen kept at $5 \,m$ away from the slit. What should be the slit width for the ray optics approximation to be valid (in $\,mm$)?