Wavelength

Formula

Description

The wavelength of an electromagnetic wave is inversely proportional to its frequency, with the speed of light (approximately 3 × 10^8 m/s in vacuum) as the constant of proportionality. This relationship is fundamental to antenna design, where antenna dimensions are typically fractions or multiples of the wavelength. For example, a quarter-wave antenna for 2.4 GHz WiFi is about 3.1 cm long. Wavelength also determines how signals interact with objects: signals with wavelengths much larger than an obstacle diffract around it, while shorter wavelengths are reflected or absorbed.

Variables

• λ — Wavelength in meters (m)
• f — Frequency in hertz (Hz)
• c — Speed of light ≈ 3 × 10⁸ m/s

Practical Notes

In transmission lines and PCB traces, the effective wavelength is shorter than free space due to the dielectric constant: λ_eff = λ / √εr. At 1 GHz, the free-space wavelength is 30 cm. When trace lengths approach λ/10, transmission line effects become significant and impedance matching is required.