Question 22N.1.HL.TZ0.27

A ray of white light is normally incident on a thin layer of oil on water. The refractive index of oil is $\frac{3}{2}$ and the refractive index of water is $\frac{4}{3}$.

The wavelength of violet light in air is ${\lambda }_{\text{v}}$.

What is the minimum thickness of the thin layer of oil so that the colour of the reflected light is violet?

A.  $\frac{{\lambda }_{\text{v}}}{6}$

B.  $\frac{3{\lambda }_{\text{v}}}{4}$

C.  $\frac{{\lambda }_{\text{v}}}{2}$

D.  $\frac{{\lambda }_{\text{v}}}{3}$