Question

In the design of eyeglasses with anti-reflection coating, the most important aspect to make right is the:

Answer 1

The thickness of the coating is most important

If the coating is λ / 4 thick then there will be a phase change at the air/glass interface and no phase change at the glass/air interface (rule of reflection).

If the coating is λ / 4 thick then there will be destructive interface between light reflected from the back and the front of the lens.

Note that the wavelength of the light within the lens is (λ / n) where n is the index of refraction of the coating on the lens.