Question

For sky wave propagation of a `10 MHz` signal, what should be the minimum electron density in ionosphere?
A. `~~1.2xx10^12//m^3`
B. `~~10^6//m^3`
C. `~~10^14//m^3`
D. `~~10^22//m^3`

Answer 1

Correct Answer - A
The critical frequency `f_c=9(N_"max")^(1//2)`
`10xx10^6=9(N_"max")^(1//2)`
On squaring both sides , `therefore (10xx10^6)^2=81 (N_"max")`
`therefore N_"max" = (100/81)xx10^12=1.2xx10^12 m^3`