Question

Dicuss the radio wave propagation in ionosphere thorigh reflection and refraction.
According to 5 marks

Answer 1

Radio waves are electromagnetic waves having frequencies as high as 300 GHz to as low as 3 kHz. The wavelength ranges from 1mm to 100km. The upper region (80-1000km) of the atmosphere gets ionized by the outer space photons and cosmic rays, this region is known as the ionosphere. The atmosphere, especially ionosphere is an excellent absorptive medium for some of the wavelengths. And it reflects some of the wavelength too.

The reflective phenomenon of radio waves from ionosphere is called back scattering and if it is strong enough, waves coming from the ground can reflect back to ground for a specific angle and wavelength. This is called skywave propagation and used for long range radio communications TV and shortwave broadcast, as Earth's curvature is a blockage for line-of-sight radio communications.

The refractive phenomenon is being used for large array radio astronomy. Wavelengths from ~10cm to ~10m is refracted through the ionosphere and this helps to view the universe with a different wavelength making many obstacles like gas cloud and derbies transparent and observe background stars.