The diagram shows a signal sent from a ground dish up to a communications satellite in orbit and then back down to a second dish on the far side of the worl...
Question 1 Report
The diagram shows a signal sent from a ground dish up to a communications satellite in orbit and then back down to a second dish on the far side of the world. 
Which region of the electromagnetic spectrum is normally used for this satellite link?
Answer Details
Satellite communication links use microwaves. Microwaves have frequencies high enough to carry large amounts of data and, crucially, they can pass through the Earth's atmosphere (including clouds and rain) with relatively little absorption, making them ideal for ground-to-satellite transmissions.
Radio waves can also pass through the atmosphere but are generally used for different purposes (broadcast radio, TV); the specific application of a dish-to-satellite-to-dish link as shown in the diagram is the classic microwave scenario at IGCSE level. Ultraviolet and infra-red would be heavily absorbed or scattered by the atmosphere, making them unsuitable for this purpose.
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