A Possible Means for Making an Airplane Radar-Invisible Is to Coat

Multiple Choice

A possible means for making an airplane radar-invisible is to coat the plane with an antireflective polymer.If radar waves have a wavelength of 6.00 cm,and the index of refraction of the polymer is n = 1.68,how thick would the coating be if a 180° phase change occurs at both surfaces?

A) 17.9 mm
B) 35.7 mm
C) 8.93 mm
D) 4.46 mm
E) 25.2 mm