Q. For skywave propagation of a $10\ MHz$ signal, what should be the maximum electron density in ionosphere
A) $\sim 1.2 \times 10^{12}m^{- 3}$
B) $\sim 10^{6}m^{- 3}$
C) $\sim 10^{14}m^{- 3}$
D) $\sim 10^{22}m^{- 3}$
Explanation
(a) If maximum electron density of the ionosphere is $N_{\max}$ per $m^{3}$ then the critical frequency $f_{c}$ is given by $f_{c} = 9\left( N_{\max} \right)^{1/2}$
$\Rightarrow 10 \times 10^{6} = 9(N)^{1/2} \Rightarrow N = 1.2 \times 10^{12}m^{- 3}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.