Question

A sky wave with a frequency 55 MHz is incident on D-region of earth's atmosphere at ${45}^{\circ }$. The angle of refraction is (electron density for D-region is 400 electron/${cm}^3$)

• A. ${60}^{\circ }$
• B. ${45}^{\circ }$
• C. ${30}^{\circ }$
• D. ${15}^{\circ }$

Answer 1

The correct option is B ${45}^{\circ }$

$n_{eff}=n_0\sqrt{1-\left(\frac{80.5N}{v^2}\right)}$ = 1 $\sqrt{1-\frac{80.5\times (400\times {10}^6)}{{(55\times {10}^{}6)}^2}}\approx 1$
Also $n_{eff}=\frac{sini}{sinr}\Rightarrow sinr=sini\Rightarrow r=i={45}^{\circ }$