Wireless communication is reflected to earth’s surface by

The correct answer is C) Ionosphere. Radio waves in the HF band (roughly 3 to 30 MHz) are refracted back to earth by the ionized layers of the ionosphere, which lies about 60 to 1000 km above the surface. Solar ultraviolet and X-rays ionize its gas molecules, and the D, E and F layers bend these waves back down. This is called skywave propagation and is how shortwave broadcasting crosses continents.

• A) Troposphere: The lowest layer, up to about 12 km, holds our weather. It affects VHF and UHF signals through scattering and ducting, but it does not reflect waves back to earth in the way the question means.
• B) Stratosphere: This layer holds the ozone layer, which absorbs UV radiation. It has no role in reflecting wireless signals.
• D) Exosphere: This is the outermost, extremely thin layer, where satellites orbit. Signals pass through it rather than bouncing off it.

Mains angle: the same ionospheric behaviour explains why VHF and microwave signals pass through, which is why satellite communication uses them. Ionospheric disturbances also cause GPS errors, a point that links to space weather in current affairs.

Trap: Aspirants often pick the troposphere because it is the weather layer, or assume every wave reflects. Only certain frequencies are reflected by the ionosphere.