Q. A sky wave with a frequency 55 MHz is incident on the D-region of earth's atmosphere at$30{^\circ}$. The angle of refraction is (electron density for D-region is 400 electron/cc)
A) $60{^\circ}$
B) $15{^\circ}$
C) $45{^\circ}$
D) $30{^\circ}$
Explanation
(d) For D-region, $v = 55 \times 10^{6}\ Hz;i = 30{^\circ}$
$N = 400 \times 10^{6}\ m^{- 3}$
$\mu = \sqrt{1 - \frac{81.45N}{v^{2}}}$
$= \sqrt{1 - \frac{81.45 \times 400 \times 10^{6}}{\left( 55 \times 10^{6} \right)}} \approx 1$
Also $\mu = \frac{\sin i}{\sin r}\ \ or\ \sin{i = \mu\sin{r = \sin r}}$
or $i = r = 30{^\circ}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.