How Wave Frequency Determines Pitch and Color

I just showed you how tapping the lake harder made bigger waves — and tapping faster packed them closer together. Every wave, whether it travels through water, air, or empty space, can be described by three key measurements. Amplitude is the height of a wave from its resting position to its peak. Think of it as how 'big' or 'powerful' the wave is. For a sound wave, a large amplitude means the air is pushed and pulled more forcefully, so you hear a LOUD sound. A small amplitude produces a quiet sound. For a light wave, a larger amplitude means the wave carries more energy, making the light appear brighter. Wavelength is the distance from one peak (or crest) to the very next peak. A long wavelength means the peaks are far apart; a short wavelength means they are close together. Frequency is how many complete wave cycles pass a fixed point every second. The unit for frequency is the hertz (Hz) — one Hz equals one cycle per second. You can calculate it: frequency = number of cycles ÷ time in seconds. For example, 30 cycles in 10 seconds gives a frequency of 3 Hz. Frequency and wavelength are partners: when frequency goes up, wavelength goes down (they always multiply to give the same wave speed in a given medium). For sound, higher frequency = higher pitch. A dog whistle vibrates at very high frequency; a bass drum vibrates at very low frequency. For visible light, frequency determines exactly which color you see. Red light has the lowest frequency humans can detect, and as frequency increases the color shifts through orange, yellow, green, blue, and finally violet — the highest frequency visible to us. This is the ROYGBIV rainbow order, running from low to high frequency. Here is a trick to keep amplitude and frequency straight: Amplitude affects how strong the wave is (loud or bright). Frequency affects what kind of wave it is (high or low pitch, which color of light).