Which of the following is correct for light diverging from a point source?
(a) The intensity decreases in proportion with the distance squared.
(b) The wave front is parabolic.
(c) The intensity at the wavelength does not depend on the distance.
(d) None of these.
The refractive index of glass is 1.5 for light waves of wavelength 6000 Å in vacuum. Its wavelength in glass is
(a) 2000 Å
(b) 4000 Å
(c) 1000 Å
(d) 3000 Å
The phenomena which is not explained by Huygen’s construction of wavefront
(a) reflection
(b) diffraction
(c) refraction
(d) photo electric effect
Two coherent monochromatic light beams of intensities I and 41 superimpose. The maximum and minimum possible intensities in the resulting beam are:
(a) 5I and I
(b) 5I and 3I
(c) 3I and I
(d) 9I and I
The wavefront due to a source situated at infinity is
(a) spherical
(b) cylindrical
(c) planar
(d) circular
The idea of secondary wavelets for the propagation of a wave was first given by
(a) Newton
(b) Huygens
(c) Maxwell
(d) Fresnel
When exposed to sunlight, thin films of oil on water often exhibit brilliant colours due to the phenomenon of
(a) interference
(b) diffraction
(c) dispersion
(d) polarization
The angular resolution of a 10 cm diameter telescope at a wavelength of 5000 A is of the order of
(a) \(10^6\) rad
(b) \(10^{-2}\) rad
(c) \(10^{-4}\) rad
(d) \(10^{-6}\) rad
A double slit interference experiment is carried out in air and the entire arrangement is dipped in water. The fringe width
(a) increases
(b) decreases
(c) remains unchanged.
(d) fringe pattern disappears
An unpolarised beam of intensity \(I_0\) is incident on a pair of nicols making angle of 60° with each other. The intensity of right emerging from the pair is
The angle of incidence at which reflected light is totally polarised for reflection from air to glass (refractive index n) is
Two slits in Young’s double slit experiment have widths in the ratio 81:1. The ratio of the amplitudes of light waves is
(a) 3 :1
(b) 3 : 2
(c) 9 :1
(d) 6:1
What happens if one of the slits, say S1 in Young’s double , slit experiment-is covered with a glass plate which absorbs half the intensity of light from it?
(a) The bright fringes become less-bright and the dark fringes have a finite light intensity
(b) The bright fringes become brighter and the dark fringes become darker
(c) The fringe width decreases
(d) No fringes will be observed
What happens to the interference pattern if the two slits S1 and S2 in Young’s double experiment are illuminated by two independent but identical sources?
(a) The intensity of the bright fringes doubled
(b) The intensity of the bright fringes becomes four times
(c) Two sets of interference fringes overlap
(d) No interference pattern is observed
A single slit diffraction pattern is obtained using a beam of red light What happened if the red light is replaced by the blue light?
(a) There is no change in diffraction pattern
(b) Diffraction fringes become narrower and crowded
(c) Diffraction fringes become broader and farther apart
(d) The diffraction pattern disappear