PHYSICS · Multi-part · CBSE · Physics · Ray Optics and Optical Instruments · Ray Optics and Optical Instruments
Problem
Crown glass exhibits slight dispersion. At a wavelength of 700nm (red light) its index of refraction is 1.50, whereas at 400nm (violet light) the index is 1.54. A narrow beam of each color propagates inside a large block of crown glass and approaches a planar glass–air boundary.
(a) Calculate the critical angle for the red beam at the glass–air boundary, reporting your answer in degrees.
(b) Calculate the critical angle for the violet beam at the same boundary, also in degrees.
(c) A technician directs both beams toward the surface at an internal incidence angle of 41∘ (measured from the normal inside the glass). Determine for each color whether it emerges into the air or is totally internally reflected. Justify your conclusions quantitatively.