"Microwave refers to an electromagnetic wave with frequency higher than one gigahertz," explains Huang (one GHz is one billion cycles per second). Electromagnetic waves are all around us. A typical household telephone line operates at a few kilohertz (kHz, one thousand hertz).
「所謂微波，是指頻率高過一 GHz（即十的九次方赫茲）的電磁波，」黃文丁解釋，電磁波無所不在，一般家用電話線不過幾千赫茲，屬於低頻，無線電調頻廣播網如中廣等，收聽頻率在一百 MHz（百萬赫茲）左右，則屬於中頻。