A blue whale call and a dolphin's high-pitched click both travel through ocean water. One has a frequency of 10 Hz, the other 150,000 Hz. Despite being 15,000× different in frequency, they both travel at exactly the same speed — about 1500 m/s. Why doesn't a higher frequency wave travel faster?
A blue whale call and a dolphin's high-pitched click both travel through ocean water. One has a frequency of 10 Hz, the other 150,000 Hz. Despite being 15,000× different in frequency, they both travel at exactly the same speed — about 1500 m/s. Why doesn't a higher frequency wave travel faster?
Wave speed is a property of the medium, not of the wave itself. You can make waves of any frequency in the same material, and they'll all move at the same speed. But if the speed is fixed and you change the frequency, something else must adjust — and figuring out what that is unlocks the wave equation.
The speed of a wave in a given medium is fixed by the medium's properties. Frequency is set by the source. Wavelength then adjusts to satisfy v = fλ. Changing frequency in the same medium changes wavelength but not speed.
Think of it this way: f tells you how many wave crests the source produces per second, and λ tells you how far apart those crests are. Speed = (crests per second) × (metres per crest) = fλ. In air at 20°C, all sound travels at 343 m/s. A 440 Hz 'A' note has λ = 343/440 ≈ 0.78 m. A 880 Hz 'A' (octave higher) has λ = 343/880 ≈ 0.39 m — exactly half. Same medium, same speed, half the wavelength. Sound travels faster in denser solids because the particles are closer together and the restoring forces are stronger.