Question

The layer of the atmosphere which efficiently reflects high frequency waves particularly at night is

• A. Troposphere
• B. Stratosphere
• C. Mesosphere
• D. Thermosphere

Hint:

The ionosphere, which is part of the Thermosphere, is responsible for reflecting radio waves for long-distance communication (skywave propagation). At night, the lower absorbing layers of the ionosphere weaken, allowing HF waves to reach the higher F layer, which reflects them back to Earth efficiently.

Answer 1

The Correct Option is D

The reflection of radio waves from the upper atmosphere allows for long-distance communication. This process is known as skywave propagation.
This reflection occurs in a region of the atmosphere called the ionosphere.
The ionosphere is not a distinct layer like the others but is a region characterized by a high concentration of ions and free electrons, created by the ionization of atmospheric gases by solar radiation.
The ionosphere overlaps with the upper parts of the Mesosphere and extends throughout the Thermosphere.
The different layers of the ionosphere (D, E, F1, and F2 layers) have varying properties. The D layer absorbs HF waves during the day and disappears at night. The E and F layers are responsible for reflecting the waves.
At night, the D and E layers become much weaker, and the F1 and F2 layers combine to form a single F layer at a higher altitude. This F layer, located in the Thermosphere, is very effective at reflecting high-frequency (HF) radio waves, enabling long-distance communication.
Since the primary reflective layers at night are located within the Thermosphere, the Thermosphere is the correct answer.