Waves & Optics
Wave Speed Calculator
Calculate wave speed, frequency or wavelength using v = fλ. Covers sound in air, water and steel, light in vacuum and glass, and custom media.
Solve for
Quick examples
Wave Speed
343
m/s
Frequency
261
Hz
Wavelength
1.3142
m
Step-by-step solution
Wave equation
v = f × λRearranged for wavelength
λ = v / f = 343 / 261 = 1.3142 m
Wave speed reference values
Sound in air (20°C)
343 m/s
Sound in water (25°C)
1.481 × 10³ m/s
Sound in steel
5.960 × 10³ m/s
Sound in wood
3.900 × 10³ m/s
Light in vacuum (c)
299.792 × 10⁶ m/s
Light in glass (n≈1.5)
200.000 × 10⁶ m/s
Light in water (n≈1.33)
225.000 × 10⁶ m/s
The wave equation
The wave equation v = fλ relates the three fundamental wave properties: speed, frequency and wavelength. It applies to all wave types — sound, light, water waves, seismic waves — as long as the wave speed in the given medium is known.
For light in vacuum, v = c ≈ 3 × 10⁸ m/s regardless of frequency. For sound, the speed depends on the medium's elasticity and density — roughly 343 m/s in air at 20°C, 1480 m/s in water. For the full treatment see our article on Transverse Waves.
Why does light travel slower in glass than in vacuum?↓
Light interacts with the electrons in the glass material — it is absorbed and re-emitted repeatedly, slowing the effective propagation speed. The ratio c/v in the medium defines the refractive index n. This is why glass can bend light (Snell's law).
Does frequency change when a wave enters a new medium?↓
No — frequency is set by the source and stays constant. When a wave enters a new medium, the speed changes, so the wavelength changes proportionally (λ = v/f). This is why light bends at a boundary but its colour (frequency) stays the same.