That is not to say that radio waves cannot pack a punch from a distance.

ECONOMIST: Monitor

Unlike light waves, radio waves are not blocked by the dust clouds.

BBC: By BBC News Online Science Editor Dr David Whitehouse

In addition to the backscatter machines, the TSA has also deployed about 260 millimeter-wave machines which use radio waves and do not emit X-rays.

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Also, since radio waves sometimes arrive at your device not directly from the radio tower but rather by being bounced off a building or hill, these signals may be much lower in signal strength than if you had a clear line of sight view to the cell site.

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