A Glass (N = 1 $\lambda$ Is the Wavelength of the Light in the Film, the Film

Multiple Choice

A glass (n = 1.6) lens is coated with a thin film (n = 1.3) to reduce reflection of certain incident light.If $\lambda$ is the wavelength of the light in the film, the least film thickness is:

A) "less than $\lambda$ /4"
B) " $\lambda$ /4"
C) " $\lambda$ /2"
D) " $\lambda$ "
E) "more than $\lambda$ "