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

We known that the artificial frequency of a sky wave for reflection from an ionspheric layer of the atmosphere is given by, `upsilon_c=9n^(1//2)`
where n is the number density of electrons/ `m^3`.
It is given that n `=10^(11)//m^3`
`therefore upsilon_c9xx(10^(11))^(1//2)=2.8xx10^6Hz=2.8MHz.`
Hence the wave of frequency 2 MHz will be reflected back.