The value at which the second null occurs in H-plane of rectangular aperture of a*b is given by ____
A. sin$^{-1}$(2λ/a)
B. sin$^{-1}$(λ/a)
C. sin$^{-1}$(a/2λ)
D. sin$^{-1}$(a/λ)

Answer: A
Explanation: The area the power is radiated is given by Beam-width. The beam-width between the first nulls is the FNBW. For H-plane \(\frac{ka}{2}\) sinθ=nπ
⇨ θ= sin$^{-1}$(nλ/a)
⇨ For null n=2 θ= sin$^{-1}$(2λ/a).