A gasoline film ( ) floats on water ( ) and is illuminated from above with yellow…

PHYSICS · Single correct · A Level · Physics · Waves · Waves

Problem

A gasoline film (n=1.40n = 1.40) floats on water (n=1.33n = 1.33) and is illuminated from above with yellow light of wavelength 600 nm600\,\text{nm} in air at normal incidence. What is the smallest non-zero thickness of the film that will make the reflected yellow light appear dark (destructive interference)? (a) 225 nm225\,\text{nm} (b) 110 nm110\,\text{nm} (c) 214 nm214\,\text{nm} (d) 428 nm428\,\text{nm}

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