54. For constructive interference (which is obtained for λ = 600 nm) in this circumstance, we require 222nkkLnλ==where k= some positive oddinteger and nis the index of refraction of the thin film. Rearranging and plugging in L= 272.7 nm and the wavelength value, this gives (600 nm)0.5544(272.7 nm)1.818knkL==. Since we expect n> 1, then k= 1 is ruled out. However, k = 3 seems reasonable, since it leads to n= 1.65, which is close to the “typical” values found in Table 34-1.
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