In the ionosphere layer, the lowest frequency signal that penetrates the layer upon vertical incidence is given by

In the ionosphere layer, the lowest frequency signal that penetrates t

1.	In the ionosphere layer, the lowest frequency signal that penetrates the layer upon vertical incidence is given by
A.	fL = 81 NMax
B.	fL = 81 N2Max
C.	\(f_L=√(81 N_{Max} )\)
D.	\(f_L=81√(N_{Max} )\)
Answer» D. \(f_L=81√(N_{Max} )\)