A beam of monochromatic light with a wavelength of 520nm travels through air and enters a block of crown glass that has an index of refraction of 1.52 for that wavelength. Assume the beam strikes the surface at normal incidence so that its direction does not change.
(a) Determine the frequency of the light while it is still in air. Express your answer in terahertz (THz).
(b) Calculate the speed of the light inside the crown glass.
(c) Using your results, find the wavelength of the light inside the crown glass.
(d) Explain why the quantity calculated in part (a) remains unchanged when the light enters the glass, whereas the quantities in parts (b) and (c) do change.