In sky wave communication which of the frequency will be reflected back by the ionospheric layer having electron density $$4 \times 10^6/m^3$$ ?
  • A
    $$18 \times 10^3 \,Hz$$
  • B
    $$9 \times 10^3 \,Hz$$
  • C
    $$31 \times 10^3 \,Hz$$
  • D
    $$20 \times 10^3 \,Hz$$

Solution

Frequency is given  by
$$F= 9(N)^{\dfrac{1}{2}}$$
Where N is electron density
putting values
$$F=18*10^3$$