Electromagnetic Waves: Radio, Television and Radiolocation
How an invisible wave of electric and magnetic fields carries your favourite radio station across the mountains
Big Idea: An electromagnetic wave is a self-supporting ripple of electric and magnetic fields that spreads through empty space at the enormous speed c = 3 × 108 m/s. A wire in which charges swing back and forth (an antenna driven by an oscillating circuit) launches such a wave; a distant antenna catches it. This single idea powers radio, television, mobile phones, Wi-Fi and radar.
By the end you will be able to:
- describe an electromagnetic wave as coupled oscillating E and B fields and say why it is transverse;
- use c = λf to connect speed, wavelength and frequency;
- explain how Hertz first produced EM waves and how Popov turned them into radio;
- outline how a radio signal is sent (carrier, modulation) and received (tuning by resonance, detection);
- solve simple radiolocation problems with s = ct/2.