Video answer: Waves - frequency, speed, and wavelength (newer vid)
Top best answers to the question «Why do waves have different frequencies»
AMPLITUDE AND WAVELENGTH
The amplitude or height of a wave is measured from the peak to the trough… Longer wavelengths will have lower frequencies, and shorter wavelengths will have higher frequencies ([link]). This figure illustrates waves of differing wavelengths/frequencies.
Video answer: Electromagnetic waves: wavelengths and frequencies