The electromagnetic spectrum: from radio waves to gamma rays

0:00Radio waves, light and X-rays seem so different. What do they share?

0:06They are all electromagnetic waves: changing electric and magnetic fields that carry energy.

0:13In a vacuum, or empty space, all of them travel at about 300,000 kilometres per second.

0:21Radio waves are not sound waves. Sound needs particles, so it cannot cross a vacuum. Radio waves can.

0:30Lined up in order, they form the electromagnetic spectrum.

0:34From left to right: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.

0:44Wavelength is the distance from one crest, or top, of a wave to the next.

0:50Visible light, the only part we can see, is a narrow slice.

0:56It runs from about 700 nanometres for red to 400 for violet. A nanometre is a billionth of a metre.

1:04Across the band, wavelength gets shorter from left to right.

1:09Frequency is how many waves pass a point each second, measured in hertz.

1:15All travel at the same speed, so shorter waves pass more often: frequency rises.

1:22The energy they carry rises too.

1:25Radio waves carry radio and TV, microwaves heat food, infrared works TV remotes, and visible light lets us see.

1:35Ultraviolet kills germs, X-rays show bones, and gamma rays treat cancer.

1:41Ultraviolet, X-rays and gamma rays can damage living cells.

1:46From radio to gamma, wavelength shrinks while frequency and energy rise.