PAPER III: OPTICS UNIT-I Interference Concept of Spatial and Temporal Coherence, coherence length, coherence time, Definition and propagation of a wavefront, Huygen's principle of secondary wavelets. Young's double slit experiment. Types of interference, interference by division of wavefronts: Fresnel's Biprism, Measurement of wavelength A and thickness of a thin transparent sheet, Interference by division of amplitude: Interference in thin films of constant thickness in transmitted and reflected waves. Interference produced by a wedge shaped film, Newton's rings, Determination of wavelength and refractive index u by Newton's Rings: fringes of equal inclination (Haidinger fringes) and equal thickness (Fizeau fringes), Michelson's Interferometer, shape of fringes, Measurement of wavelength, dif...