Defining Wave Speed
Wave speed, also known as wave velocity, measures how fast a wave disturbance propagates through a medium or through space over a given time. It describes the rate at which the energy carried by the wave travels, not the speed of individual particles in the medium, which typically oscillate in place.
Calculating Wave Speed with Wavelength and Frequency
The speed of a wave (v) is fundamentally determined by its wavelength (λ) and its frequency (f) through the equation: v = λ × f. Wavelength is the distance between two consecutive identical points on a wave, while frequency is the number of complete wave cycles that pass a point per unit of time. This relationship holds true for all types of waves, from sound waves to light waves.
Factors Influencing Wave Speed
The speed of a wave is primarily dependent on the properties of the medium through which it travels. For mechanical waves (like sound), factors such as the medium's density, elasticity, and temperature play a crucial role. For electromagnetic waves (like light), the wave speed changes depending on the refractive index of the medium, slowing down in denser optical materials compared to a vacuum.
Practical Examples of Wave Speed
A common example is the speed of sound, which is approximately 343 meters per second in dry air at 20°C but is much faster in water (around 1500 m/s) and even faster in solids. The speed of light in a vacuum is a universal constant, approximately 299,792,458 meters per second, but it slows down when passing through materials like glass or water, leading to phenomena like refraction.