In short wave communication, waves of which of the following frequencies will be reflected back by the ionospheric layer having electron density `10^(11)m^(-3)`

Options

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

Answer

a

Explanation

Critical frequency.`f_(c)=9(N_(max)^(1//2))`
=`9(10^(11))^(1//2)=2.8xx10^(6)Hz`=2.8MHz
The wave of frequency 2 MHz will be reflected by the ionosphere.