What Minimum Thickness of Oil $(\mathrm{n}=1.50)$ On the Surface of Water $(\mathrm{n}=1.33)$

Multiple Choice

What minimum thickness of oil $(\mathrm{n}=1.50)$ on the surface of water $(\mathrm{n}=1.33)$ would give destructive interference for $550 \mathrm{~nm}$ light at normal incidence?

A) $78.0 \mathrm{~nm}$
B) $92.0 \mathrm{~nm}$
C) $80.0 \mathrm{~nm}$
D) $275 \mathrm{~nm}$
E) $183 \mathrm{~nm}$