The diagrams below show the intensity distribution in diffraction of light of two sources. In which of the following cases the sources are just resolved?

$A$ student is jogging on a straight path with a speed of $5.4 \,km/h$. Perpendicular to the path is a pipe with its opening $8 \,m$ from the road (see figure). The diameter of the pipe is $0.45 \,m$. At the other end of the pipe is a speaker emitting sound of $1280 \,Hz$ towards the opening of the pipe. As the student passes in front of the pipe,she hears the speaker sound for $T$ seconds. $T$ is in the range (Take speed of sound $= 320 \,m/s$):

In Fraunhofer diffraction,draw the graph of the intensity of light on the screen versus the diffraction angle $\theta$ and write its characteristics.

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 ....... $\mathring{A}$.

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.

For an aperture of $5 \times 10^{-3} \ m$ and a monochromatic light of wavelength $\lambda$, the distance for which ray optics becomes a good approximation is $50 \ m$, then $\lambda=$ (in $\text{Å}$)