Electromagnetic wave interaction with matter - Higher

Refraction in the atmosphere

The Earth's surface is curved. In order to send radio waves over long distances they must be reflected from the ionosphere, which is part of the Earth's atmosphere.

Graphic of the Earth and the atmosphere. It shows how radio waves are reflected from a charged layer of the upper atmosphere and received. Microwaves pass through the atmosphere.Low frequency radio waves will reflect off the ionosphere and higher frequency waves will pass through it

Absorption and transmission of waves

As well as being reflected or refracted, waves can also be absorbed or transmitted when they move from one material to another.

For example, radio waves are transmitted by walls - this explains why these signals can be detected by radios inside a person's house. However, visible light rays are absorbed by walls, which is why windows are needed to allow the Sun's rays into a building. Walls also absorb ultraviolet rays, which is why people don't get sunburnt indoors. The atmosphere absorbs X-rays and gamma rays from space which can cause harm to the human body.

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