Wavelength (λ) and frequency (f) are inversely related for any wave: c = λf, where c = wave speed.
Electromagnetic Spectrum
- Radio waves: λ > 1 m, f < 300 MHz
- Visible light: λ = 380–700 nm (violet → red)
- X-rays: λ = 0.01–10 nm
- Gamma rays: λ < 0.01 nm
Speed of Light
In vacuum: c = 3×10⁸ m/s. For light: λ = c/f. Red light (f=4.3×10¹⁴ Hz) has λ ≈ 700 nm.
Why Radio Waves Bend Around Obstacles But Light Doesn't
Longer wavelengths diffract (bend around obstacles) more easily than shorter ones — this is why AM radio (very long wavelength) can reach behind hills and buildings where visible light (extremely short wavelength) is completely blocked, casting a sharp shadow. The same principle explains why bass frequencies travel through walls far better than treble.
Doppler Effect
When a wave source moves toward you, wavelength compresses and frequency rises (higher pitch, or blue-shifted light); moving away stretches wavelength and lowers frequency (lower pitch, red-shifted light). This is why a passing ambulance siren changes pitch, and how astronomers detect that distant galaxies are moving away from us.