The time required for the light to pass through a glass slab (refractive index = 1.5) of thickness 4 mm is (c = 3 x 10⁸ ms^-1, speed of light in free space)

• 10^-11 s

• 2 × 10^-11 s

• 2 × 10¹¹ s

• 2 × 10^-5 s

A prism having refractive index 1.414 and refracting angle 30° has one of the refracting surfaces silvered. A beam of light incident on the other refracting surface will retrace its path, if the angle of incidence is

• 0°

• 30°

• 60°

• 45°

A planoconvex lens has a maximum thickness of 6 cm. When placed on a horizontal table with the curved surface in contact with the table surface, the apparent depth of the bottom most point of the lens is found to be 4 cm. If the lens is inverted such that the plane face of the lens is in contact with the surface of the table, the apparent depth of the centre of the plane face is found to be $\left(\frac{17}{4}\right)$ cm. The radius of curvature of the lens is

• 68 cm

• 75 cm

• 128 cm

• 34 cm

Two thin lenses have a combined power of +9D. When they are separated by a distance of 20 cm, their equivalent power becomes $+ \frac{27}{5} \mathrm{D}$. Their individual powers (in dioptre) are

• 1, 8

• 2, 7

• 3, 6

• 4, 5

Two monochromatic light waves of amplitudes 3A and 2A interfering at a point have a phase difference of 60°. The intensity at that point will be proportional to

• 5 A²

• 13 A²

• 7 A²

• 19 A²

Consider the following statements in case of Young's double slit experiment.

1. A slit S is necessary if we use an ordinary extended source of light.
2. A slit S is not needed if we use an ordinary but well collimated beam of light.
3.  A slit S is not needed if we use a spatially coherent source of light.

Which ofthe above statements are correct ?

• (1), (2) and (3)

• (1) and (2)

• (2) and (3)

• (1) and (3)

A parallel beam of light ofwavelength 6000 $\stackrel{\circ }{\mathrm{A}}$ gets diffracted by a single slit of width 0.3 mm. The angular position of the first minima of diffracted light is

• 2 × 10^-3 rad

• 3 × 10^-3 rad

• 1.8 × 10^-3 rad

• 6 × 10^-3 rad

48.

The critical angle of a certain medium is ${\sin }^{-1} \left(\frac{3}{5}\right)$. The polarizing angle of the medium is

• ${\sin }^{-1} \left(\frac{4}{5}\right)$

• ${\tan }^{-1} \left(\frac{5}{3}\right)$

• ${\tan }^{-1} \left(\frac{3}{4}\right)$

• ${\tan }^{-1} \left(\frac{4}{3}\right)$

The photoelectric threshold wavelength for silver is M. The energy of the electron ejected from the surface of silver by an incident wavelength λ (λ < λ₀) will be

• hc (λ₀ − λ)

• $\frac{\mathrm{hc}}{{\mathrm{\lambda }}_0 - \mathrm{\lambda }}$

• $\frac{\mathrm{h}}{\mathrm{c}} \left(\frac{{\mathrm{\lambda }}_0 - \mathrm{\lambda }}{{\mathrm{\lambda \lambda }}_0}\right)$

• $\mathrm{hc} \left(\frac{{\mathrm{\lambda }}_0 - \mathrm{\lambda }}{{\mathrm{\lambda \lambda }}_0}\right)$

Rutherford's atomic model could account for

• stability of atoms

• origin of spectra

• the positive charged central core of an atom

• concept of stationary orbits