A thin oil film (index of refraction ) floats on water ( )

PHYSICS · Single correct · AP · Physics 2: Algebra-based · Waves Sound and Physical Optics · Waves Sound and Physical Optics

Problem

A thin oil film (index of refraction n=1.40n = 1.40) floats on water (n=1.33n = 1.33). Monochromatic light of wavelength λ\lambda in air is incident normally from above. For the reflected light to exhibit constructive interference, which thickness condition must the oil satisfy? (a) 2nt=(m+14)λ2 n t = \left(m + \tfrac{1}{4}\right)\lambda (b) 2nt=mλ2 n t = m\lambda (c) 2nt=(m+12)λ2 n t = \left(m + \tfrac{1}{2}\right)\lambda (d) nt=(m+12)λn t = \left(m + \tfrac{1}{2}\right)\lambda

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