1. If a thin film of soap (n = 1.39) hanging in air reflects predominantly red light of wavelength 681 nm, what is the minimum thickness of the film? Answer:( Not yet correct, tries 1/15 Submit All Answers Hint: Remember the condition for an interference maximum for this situation (refraction off a medium with a larger index of refraction). Pathlength difference PD = 2t (m + 1/2)(lambda/n). What is the relation between PD and the thickness of the film? Is the wavelength in all media the same? 2. If this film is placed on a sheet of glass (n = 1.57), what is the longest wavelength that will be predominantly reflected?

1. If a thin film of soap (n = 1.39) hanging in air reflects predominantly red light of wavelength 681 nm, what is the minimum thickness of the film? Answer:( Not yet correct, tries 1/15 Submit All Answers Hint: Remember the condition for an interference maximum for this situation (refraction off a medium with a larger index of refraction). Pathlength difference PD = 2t (m + 1/2)(lambda/n). What is the relation between PD and the thickness of the film? Is the wavelength in all media the same? 2. If this film is placed on a sheet of glass (n = 1.57), what is the longest wavelength that will be predominantly reflected?