Question

If the maximum electron density for E layer in ionosphere is 9 × 10⁶ electrons/cm³, then its critical frequency is
1. 81 MHz
2. 9 MHz
3. 27 MHz
4. 54 MHz

Answer 1

Correct Answer - Option 3 : 27 MHz

Concept:

The limiting frequency at or below which the wave component is reflected and above which it penetrates through an ionospheric layer depends upon the electron density of the ionosphere:

\({{f}_{c}}=9\sqrt{{{N}_{max}}}\)

Where f_c is in Hz.

and N_max = Maximum electron density/m3

Calculation:

Given, Nmax = 9 × 106 electrons/cm3

= 9 × 1012 electrons/m3

\(f_c =9\times\sqrt{9\times 10^{12}}~Hz\)

= 27 MHzfc1=91011=9×10510==\(f_c=9\times {\sqrt{9\times 10^{12}}}\)=0.910‾‾‾= 27 MHz