A broad beam of light of wavelength 600 nm is sent directly downward through the glass plate (n = 1.41). That plate and a plastic plate (n = 1.24) form a thin wedge of air that acts as a thin film. An observer looking down through the top plate sees the fringe pattern, with 7 dark fringes, having two centered on the ends. (a) What is the thickness (in m) of wedge at the right end? (b) How many dark fringes will the observer see if the air between the plates is replaced with a liquid with n = 1.35?

A broad beam of light of wavelength 600 nm is sent directly downward through the glass plate (n = 1.41). That plate and a plastic plate (n = 1.24) form a thin wedge of air that acts as a thin film. An observer looking down through the top plate sees the fringe pattern, with 7 dark fringes, having two centered on the ends. (a) What is the thickness (in m) of wedge at the right end? (b) How many dark fringes will the observer see if the air between the plates is replaced with a liquid with n = 1.35?