Question

In the diagram shown here, EM Waves, sent from a transmitting antenna, are being received back on the earth via ionospheric reflection. One can say that the

(1) (Relative) refractive index, of the ionospheric layer, between the E and F layers in less than (1/sin α).

(2) (Relative) refractive index, of the ionospheric layer, between the E and F layers, is, of the order of, or more than (1/sin α).

(3) Rays (2) and (3) are incident at angles greater than the critical angles for the layers F₁ and F₂ . 

(4) There are no ions at all, in the ionospheric layers above the layer F₁, that can cause ionospheric reflection.

Answer 1

Correct option:  (2)

Explanation: 

The bending of EM waves, via ionospheric reflection, is similar to the phenomenon of total internal reflection. For TIR, we have,

µ = (1/sin θ_c )

where θ_C is the critical angle for the given pair of media. 

For µ less than  (1/sin θ_c )  these can be no TIR when the angle of incidence is θ_c or less.

Hence statements (1) and (3) are incorrect. Statement (4) is also incorrect as the layers mentioned have a relatively low ion..............