um 4...\" Pumas A ray of light is incident at an angle of 51.1 on the surface of a piece of crown glass whose index of refraction is 1.52 . What is the angle of reection? Answer in units of . WU 1U.\" PULIIIJH Laser scientists can now generate pulses of light as short as 1fs = I'Dms. One of the great diiculties in working with such short pulses is that many EM waves of different equencies must be superposed to create the pulse. Because real optical elements Like lenses and prisms are made of real materials for which the index of refraction is wavelength- dependent i.e., the material is dispersive, parts of the pulse with different equencies travel through the optical elements at dif- ferent speeds and become separated, so the pulse spreads out. Consider a short laser pulse which is normally incident on a piece of crown glass which is L = 7.88 mm thick. The index of refraction for a wavelength of )'3 = 407 nm in the blue part of the pulse is n5. = 1.53, and the index of refraction for a wavelength of AR = 637 nm in the red part of the pulse is HR = 1.51. How much sooner does the red part of the pulse arrive at the end of the piece of glass than the blue part? Answer in units of fs