In short wave communication, waves of which of the following frequencies will be reflected back by the ionoshperic layer having electron density `10^11 " per " m^3`

Options

A. 2 MHz
B. 10 MHz
C. 12 MHz
D. 18 MHz

Answer

A

Explanation

`N_(max)=(f_(c)^(2))/(81)=((10xx10^(6))^(2))/(81)~~1.2xx10^(12)m^(-3)`