A) 1.50cm
B) 3.00cm
C) 0.50cm
D) None of these
Correct Answer: C
Solution :
[c] Treating the anti-reflectance coating like a camera-lens coating, one can obtain for its thickness t: \[2t=\left( m+\frac{1}{2} \right)\frac{\lambda }{n}\], \[m=0,\,\pm 1,\,\pm 2\] ...... (i) Condition (1) is the condition for the destructive interference for the normally incident and reflected electromagnetic wave. The minimum thickness of the coat refers to m= 0. This gives for the thickness: \[t=\frac{\lambda }{4n}=\frac{3.00}{4(1.5)}cm=0.500cm\] This anti-reflectance coating could be easily countered by changing the wavelength of the radar to L50 cm now creating maximum reflection.
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