In a Fraunhofer diffraction pattern,the slit width is $0.5 \ mm$ and the screen is at $2 \ m$ away from the lens. If the wavelength of the light used is $5500 \ Å$,then the distance between the first minima on either side of the central maximum is (assume $\theta$ is small and measured in radians). (in $mm$)

In Fraunhofer diffraction pattern, slit width is $0.2 \, mm$ and screen is at $2 \, m$ away from the lens. If wavelength of light used is $5000 \, \mathring{A}$, then the distance between the first minimum on either side of the central maximum is (assume $\theta$ is small and measured in radians).

$A$ 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 $= 320 \,m/s$):

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

For Fraunhofer diffraction to occur:

What is Fresnel distance? Write its formula.