Question

In short wave communication, waves of which of the following frequencies will be reflected back by the ionospheric layer having electron density 10¹¹ m^-3?

(a) 2 MHz 

(b) 10 MHz 

(c) 12 MHz 

(d) 18 MHz

Answer 1

(a) 2 MHz 

Critical frequency, 

f_c = 9 (N_max)^1/2 

= 9(10¹¹)^1/2 = 2.8 x 10⁶ Hz = 2.8 MHz

∴ The wave of frequency 2 MHz will be reflected by the ionosphere.