Diffraction Questions

A parallel beam of fast moving electrons is incident normally on a narrow slit. If the speed of electrons is increased:

A beam of light of $\lambda =600\text{nm}$ from a distant source falls on a single slit $1\text{mm}$ wide and the resulting diffraction pattern is observed on a screen $2\text{m}$ away. The distance between first dark fringes on either side of the central bright fringe is:

At the first minimum adjacent to the central maximum of a single-slit diffraction pattern, the phase difference between the Huygen's wavelet from the edge of the slit and the wavelet from the midpoint of the slit is:

In a diffraction pattern due to a single slit of width $a$, the first minimum is observed at an angle $30^{\circ }$ when light of wavelength $5000\text{A˚}$ is incident on the slit. The first secondary maximum is observed at an angle of:

A linear aperture whose width is $0.02\text{cm}$ is placed immediately in front of a lens of focal length $60\text{cm}$. The aperture is illuminated normally by a parallel beam of wavelength $5\times 10^{-5}\text{cm}$. The distance of the first dark band of the diffraction pattern from the centre of the screen is: