What is the phase excitation difference in end-fire array with array s

1.	What is the phase excitation difference in end-fire array with array spacing d at =0 ?
A.	(- frac{2 }{ } d )
B.	( frac{2 }{ } d )
C.	(- frac{ }{ } d )
D.	( frac{ }{ } d )
Answer» B. ( frac{2 }{ } d )

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