Question 1: Answer any four parts from the given questions.
a) The sodium lamp used in a physics laboratory gives out light uniformly. Assume that the lamp uses 60 W. Compute the magnitude of electric field.
b) Explain polarization of light by reflection. How does degree of polarization differ with angle of incidence of light?
c) Describe the fundamental differences between holography and photography.
d) Depict spatial evolution of Fresnel diffraction pattern.
e) Discuss the concept of missing orders with particular reference to double slit diffraction pattern.
Question 2:
a) A laser beam is directed upward to make a tiny blackened glass sphere of mass 10−9 kg and diameter 20µm afloat in air. Compute the intensity of the laser beam.
b) Get the expression for shift in fringes when a thin transparent sheet is introduced in the path of one of the waves in a double slit interference experiment.
Question 3:
a) Describe Fraunhofer diffraction pattern produced by N identical vertical slits. Obtain expression for intensity distribution and plot it for N = 6 with a = 4b.
b) Consider a diffraction grating having 15000 lines to an inch. Compute the dispersion suffered due to diffraction by red (λR = 700nm) and violet (λV = 400 nm) colors in the first order spectrum when white light source is used to get diffraction pattern. How this spread is influenced in the second and third order spectra?
Question 4:
a) Describe Rayleigh’s criterion for resolving power of an optical instrument. Obtain an expression for resolving power of a microscope.
b) A typical thin film of refractive index 1.33 and thickness 5.1 x 10 m−6 is illuminated by a point source of while light. Light is made to fall:
i) Normally and at 60°.
Which colors will appear in the reflected light?
Question 5:
a) Describe three significant practical applications of holography.
b) Compute in ratio of stimulated emission and spontaneous emission at an operating temperature of 1100 K, if the wavelength of emitted light is 550 nm. Do such conditions correspond to a laser?
c) State the characteristics of different kinds of optical fibers. Depict their refractive index profiles and propagation of light via them.