A Lens with a Refractive Index of 1 $\lambda$ Denotes the Wavelength of the Incident Light in Air, What

Multiple Choice

A lens with a refractive index of 1.5 is coated with a material of refractive index 1.2 in order to minimize reflection. If $\lambda$ denotes the wavelength of the incident light in air, what is the thinnest possible such coating?

A) 0.5 $\lambda$
B) 0.416 $\lambda$
C) 0.3 $\lambda$
D) 0.208 $\lambda$
E) 0.25 $\lambda$