Final answer:
The thickness of the coating should be much smaller than the wavelength of the radar, not equal to it, which is an unreasonable assumption.
Step-by-step explanation:
In order to inhibit the reflection of radar with a wavelength of 4.00 cm, the coating thickness should be equal to a quarter of the wavelength, which is 1.00 cm.
What is unreasonable about this result is that the thickness of the coating should be much smaller than the wavelength of the radar, not equal to it. This assumption is therefore inconsistent.
The primary topic of this question is the interaction of waves with materials, specifically the reflection of radar waves by a coating on a plane.