Vanessa wants to increase the energy efficiency of her house bycoating the windo

Question

Vanessa wants to increase the energy efficiency of her house bycoating the windows with a thin plastic film to reflect as muchlight as possible. The index of refraction of the windowglass is 1.52, and the index of refraction of the plastic film is1.85.
a. How thick should the film be if it is to be most reflectivefor the light with wavelength 550 nm? b. It's actually too difficult to manufacture and handle filmthat's as thin as calculated in part a. What is the nextgreatest thickness that the film can be?
a. How thick should the film be if it is to be most reflectivefor the light with wavelength 550 nm? b. It's actually too difficult to manufacture and handle filmthat's as thin as calculated in part a. What is the nextgreatest thickness that the film can be?

Explanation / Answer

you want constructive interference with a relative phase shiftso .     2tn = (1/2)         or .    t = / 4n = 550 /4 * 1.85 =    74.3 nm . The next thickness would be given by .     2tn = (3/2)        or .    t = 3 / 4n =        223nm

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