Convert between wavelength, frequency, and wave speed using v = f × λ — for light, sound, and radio waves.
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Every wave follows the same fundamental relationship: wave speed equals frequency multiplied by wavelength (v = f × λ). This applies to light, sound, water waves, and radio signals alike — only the speed of travel changes depending on the medium.
For a fixed wave speed, higher frequency means shorter wavelength, and lower frequency means longer wavelength. This is why radio waves (low frequency) have wavelengths measured in metres, while visible light (high frequency) has wavelengths measured in nanometres.
Light travels through a vacuum at roughly 299,792,458 metres per second — the universal speed limit. Sound, by contrast, travels much slower and only through a physical medium like air, water, or solid material, with its speed changing significantly depending on what it's passing through.
Sound travels by vibrating particles, and denser, more tightly packed mediums transmit those vibrations faster. Water molecules are much closer together than air molecules, so sound moves roughly four times faster in water than in air.
Visible light spans roughly 380 to 750 nanometres in wavelength, from violet at the short end to red at the long end. Wavelengths shorter than violet are ultraviolet, and those longer than red are infrared.
Radio waves travel at the speed of light, so a station broadcasting at 100 MHz has a wavelength of about 3 metres (300,000,000 ÷ 100,000,000). Lower-frequency AM stations have much longer wavelengths than higher-frequency FM stations.