What is Wave Velocity?
Wave velocity is simply the speed at which a wave travels through a medium.
More formally, it tells you how fast a disturbance (like sound, light, or water ripples) moves from one point to another.
Key Idea
Wave velocity depends on two main factors:
- The frequency of the wave
- The wavelength (distance between two consecutive crests or compressions)
These are related by the formula:
v = f × λ
Where:
- v = wave velocity (m/s)
- f = frequency (Hz)
- λ = wavelength (meters)
Examples
- Sound waves travel faster in solids than in air
- Light waves travel fastest in a vacuum
- Water waves move at speeds depending on depth and gravity
Simple Way to Think About It
If you drop a stone in water, the ripples spreading outward have a certain speed—that speed is the wave velocity.
If you want, I can show you how it changes in different media or solve a sample problem.
You can apply the formula v = f × λ to light—there’s no exception here. The confusion usually comes from how frequency and wavelength behave in different media.
The formula v = fλ is always valid for waves, including light.
When light moves from one medium to another (like air → water):
- Frequency (f) stays the same
- Wavelength (λ) changes
- Therefore, velocity (v) changes
So the formula still works perfectly—you just have to use the new wavelength in that medium.
We also use:
v = c / n
This tells you how the speed changes due to the medium. If you combine both ideas:
v = fλ = c / n
- In vacuum: v = c = fλ
- In a medium: v decreases → λ decreases → f stays constant
Summary
You are applying f × λ for light—the key is remembering that wavelength adjusts when speed changes, not frequency.
If you want, I can show a quick numerical example to make this clearer.