71.

A ground receiver in line-of-sight communication cannot receive direct waves due to

• its low frequency

• curvature of earth

• its high intensity

• smaller antenna

In an amplitude modulation with modulation index 0.5, the ratio of the amplitude of the carrier wave to that of the side band in the modulated wave is

• 4 : 1

• 1 : 1

• 1 : 2

• 2 : 1