Question

What is the ratio of critical frequency for reflection of radiowaves from $E,F_1$ and $F_2$ layers in ionosphere if the electron densities are $2\times {10}^{11},3\times {10}^{11}$ and $8\times {10}^{11}{m}^{-3}$ respectively?

• A. $1:2:3$
• B. $1:1.5:3$
• C. $1.41:1.73:2.83$
• D. $1.52:1.52:1.89:2.60$

Answer 1

The correct option is C $1.41:1.73:2.83$

Critical frequency, $v_c=9\sqrt{N_{max}}$
i.e., $v_c\propto \sqrt{N_{max}}$
$\therefore v_{C_E}:v_{C_{F_1}}:V_{C_{F_2}}$
$=\sqrt{2\times {10}^{11}}:\sqrt{3\times {10}^{11}}:\sqrt{8\times {10}^{11}}$
$=\sqrt{2}:\sqrt{3}:\sqrt{8}=1.41:1.73:2.83$.