In the Young's double slit experiment, the central maxima is observed to be I_0.  If one of the slits is covered, then the intensity at the central maxima will become

• $\frac{{\mathrm{I}}_0}{2}$

• $\frac{{\mathrm{I}}_0}{\sqrt{2}}$

• $\frac{{\mathrm{I}}_0}{4}$

• ${\mathrm{I}}_0$

Two identical light waves, propagating in the same direction, have a phase difference 6. After they superpose the intensity of the resulting wave will be proportional to

•  $\cos \mathrm{\delta }$

• $\cos \left(\frac{\mathrm{\delta }}{2}\right)$

• ${\cos }^2 \left(\frac{\mathrm{\delta }}{2}\right)$

• ${\cos }^2\mathrm{\delta }$

In Young's double slit experiment, the fringe width is β. If the entire arrangement is placed in a liquid of refractive index n, the fringe width becomes

• nβ

• $\frac{\mathrm{\beta }}{\mathrm{n} + 1}$

• $\frac{\mathrm{\beta }}{\mathrm{n} - 1}$

• $\frac{\mathrm{\beta }}{\mathrm{n}}$

The light beams of intensities in the ratio of 9 : 1 are allowed to interfere. What will be the ratio of the intensities of maxima and minima ?

• 3 : 1

• 4 : 1

• 25 : 9

• 81 : 1

In Young's double slit experiment the two slits are d distance apart. Interference pattern is observed on a screen at a distance D from the slits. A dark fringe is observed on the screen directly opposite to one of the slits. The wavelength of light is

• $\frac{{\mathrm{D}}^2}{2\mathrm{d}}$

• $\frac{{\mathrm{d}}^2}{2\mathrm{D}}$

• $\frac{{\mathrm{D}}^2}{\mathrm{d}}$

• $\frac{{\mathrm{d}}^2}{\mathrm{D}}$

In Young's double slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelengths λ₁ = 12000 $\stackrel{\circ }{\mathrm{A}}$ and λ₂ = 10000 $\stackrel{\circ }{\mathrm{A}}$. At what minimum distance from the common central bright fringe on the screen 2 m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other ?

• 8 mm

• 6 mm

• 4 mm

• 3 mm

A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance froni the slit. If the speed of the electrons is increased, then which of the following statements is correct ?

• Diffraction pattern is not observed on the screen in the case of electrons

• The angular width of the central maximum of the diffraction pattern will increase

• The angular width of the central maximum will decrease

• The angular width of the central maximum will be unaffected

Two coherent monochromatic beams of intensities I and 41 respectively are superposed. The maximum and minimum intensities in the resulting pattern are

• 5I and 3I

• 9I and 3I

• 4I and I

• 9I and I

A thin plastic sheet of refractive index 1.6 is used to cover one of the slits of a double slit arrangement. The central point on the screen is now occupied by what would have been the 7th bright fringe before the plastic was used. If the wavelength of light is 600 nm, what is the thickness (in µm) of the plastic sheet ?

• 7

• 4

• 8

• 6

Find the right condition(s) for Fraunhoffer diffraction due to a single slit.

• Source is at infinite distance and the incident beam has converged at the slit.

• Source is near to the slit and the incident beam is parallel

• Source is at infinity and the incident beam is paralle

• Source is near to the slit and the incident beam has converged at the slit