What minimum thickness of oil ( $\mathrm{n}=1.50)$ on the surface of water $(\mathrm{n}=1.33)$ would give constructive interference for $550 \mathrm{~nm}$ light at normal incidence?
A) $92.0 \mathrm{~nm}$
B) $183 \mathrm{~nm}$
C) $80.0 \mathrm{~nm}$
D) $275 \mathrm{~nm}$
E) $78.0 \mathrm{~nm}$

Question

Quizplus · Accepted Answer

Constructive interference occurs when the thickness $ t $ of the oil film satisfies $ 2nt = m\lambda $, where $ m $ is an integer. For minimum thickness, $ m = 1 $, so $ t = \frac{\lambda}{2n} = \frac{550 \, \text{nm}}{2 \times 1.50} = 92.0 \, \text{nm} $.

What Minimum Thickness of Oil n=1.50)\mathrm{n}=1.50)n=1.50) On the Surface of Water

What Minimum Thickness of Oil $\mathrm{n}=1.50)$ On the Surface of Water