Wave Optics

A fish at a depth of 12 cm in water is viewed by an observer on the bank of a lake. To what height the image of the fish is raised ?

• 9 cm

• 12 cm

• 3.8 cm

• 3 cm

A ray of light is incident at 50° on the middle of one of the two mirrors arranged at an angle of 60° between them. The ray then touches the second mirror, gets reflected back to the first mirror, making an angle of incidence

• 50°

• 60°

• 70°

• 80°

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