Thin Film Problem: Find Minimum Thickness for Light Transmission

[physicist10]

Homework Statement

A glass (Refractive index 1.33) is coated with a thin film. (Refractive index 1.50)

Find the minimum thickness of the film, if the glass is to transmit light of wavelength λ.

Homework Equations

The Attempt at a Solution

Light reflected from the upper surface of the film will suffer phase difference. That's all I know about this problem. Are we looking for constructive interference or destructive interference?

 

[physicist10]

No help?

 

[Redbelly98]

It sounds like they probably want 100% transmission, so constructive interference for transmission, destructive for reflection.