2. (a) In the Fresnel's biprism experiment, a biprism of refractive index 1.73 and with apex angles of 0.85° and 0.75° is used to form interference fringes. Find the fringe width for the light of wavelength 656.3 nm when the distance between the slit and the biprism is 25 cm and that between the biprism and screen is 75 cm. (b) Determine two least possible thicknesses of a film to be coated on a glass surface (µ = 1.54) such that no normally incident light of wavelength 540 nm is reflected. (c) A planoconvex lens is placed on a planoconcave lens. The radius of curvature of lower surface of the upper lens is 50 cm and upper surface of the lower lens is 100 cm. The waves reflected from the upper and lower surface of the air film interfere to produce Newton's rings. Calculate the radii of dark rings. Assume 2= 600 nm. арех

2. (a) In the Fresnel's biprism experiment, a biprism of refractive index 1.73 and with apex angles of 0.85° and 0.75° is used to form interference fringes. Find the fringe width for the light of wavelength 656.3 nm when the distance between the slit and the biprism is 25 cm and that between the biprism and screen is 75 cm. (b) Determine two least possible thicknesses of a film to be coated on a glass surface (µ = 1.54) such that no normally incident light of wavelength 540 nm is reflected. (c) A planoconvex lens is placed on a planoconcave lens. The radius of curvature of lower surface of the upper lens is 50 cm and upper surface of the lower lens is 100 cm. The waves reflected from the upper and lower surface of the air film interfere to produce Newton's rings. Calculate the radii of dark rings. Assume 2= 600 nm. арех