Final answer:
A nonreflective coating designed for a single wavelength and perpendicular incidence will not have the same effect on other wavelengths and incident directions, resulting in less effective or different types of interference.
Step-by-step explanation:
For a nonreflective coating that is optimized for a single wavelength and perpendicular incidence, other wavelengths and incident angles will not experience the same degree of destructive interference.
This is because the conditions for destructive interference, which involve the path length difference equating to a half-integral multiple of the wavelength, are specifically tailored to that single wavelength and angle.
If the wavelength changes or the light hits the coating at a different angle, the path length difference will no longer match the necessary condition for destructive interference for those new conditions. Instead, you will observe partial destructive interference, less effective interference, or even constructive interference depending on the specific wavelength and angle of incidence.