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What is the minimum thickness of a soap film needed fro constructive interference in reflected light, if the light incident on the film is\mathrm{ 750 \mathrm{~nm}} ? Assume that the index for the film is \mathrm{\mathrm{n}=1.33 :}

Option: 1

282 nm


Option: 2

70.5 nm


Option: 3

141 nm


Option: 4

387 nm


Answers (1)

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\mathrm{\begin{aligned} & 2 \mu \mathrm{f}=\frac{\lambda}{2} \\ & \therefore \quad \mathrm{t}_{\min }=\frac{\lambda}{4 \mu}=141 \mathrm{~nm} \end{aligned}}

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