In a vacuum, every electromagnetic wave travels at the same speed, called the speed of light:
\$c = 3.0 \times 10^8 \text{ m/s}\$
This speed is the same for radio waves, microwaves, infrared, visible light, ultraviolet, X‑rays, and gamma rays.
Think of a race track where all runners (waves) run at the same top speed, no matter how fast or slow they usually are. 🏃♂️🏃♀️
In air, the speed is almost identical – only a tiny fraction slower because the air molecules slightly “drag” the waves. For most everyday calculations, we treat the speed in air as the same as in a vacuum. 🌬️
| Region | Wavelength (nm) | Frequency (Hz) | Common Example |
|---|---|---|---|
| Radio | > 1,000,000 nm | < 3×10⁸ Hz | FM radio, TV broadcast |
| Microwave | 1,000 – 1,000,000 nm | 3×10⁸ – 3×10¹¹ Hz | Microwave ovens, Wi‑Fi |
| Infrared | 700 – 1,000,000 nm | 3×10¹¹ – 4.3×10¹⁴ Hz | Heat lamps, remote controls |
| Visible | 400 – 700 nm | 4.3×10¹⁴ – 7.5×10¹⁴ Hz | What we see with our eyes |
| Ultraviolet | 10 – 400 nm | 7.5×10¹⁴ – 3×10¹⁵ Hz | Sunburn, UV lamps |
| X‑ray | 0.01 – 10 nm | 3×10¹⁵ – 3×10¹⁸ Hz | Medical imaging, airport scanners |
| Gamma | < 0.01 nm | > 3×10¹⁸ Hz | Nuclear reactions, space telescopes |