question_answer 25)

  Two waves A and B of frequencies 2 MHz and 3 MHz, respectively are beamed in the same direction for communication via sky wave. Which one of these is likely to travel longer distance in the ionosphere before suffering total Internal reflection?

Answer:

                  We know that refractive index  of a medium is related with wavelength of wave according to relation                  and Therefore, the value of refractive index (l of a medium increases with the decrease in wavelength or increase in frequency of wave travelling through medium. For higher frequency wave, angle of refraction r is less, i.e., bending of wave is less in medium. Due to it, the condition for total internal reflection is attained after travelling longer distance by higher frequency wave. Hence 3 MHz wave will travel longer distance in the ionosphere before suffering total internal reflection.