How to Calculate Wave Speed
What is Wave Speed?
The wave equation v = fλ relates wave speed (v), frequency (f), and wavelength (λ). All electromagnetic waves travel at the speed of light in vacuum (c ≈ 3×10⁸ m/s); sound travels at ≈343 m/s in air.
Formula
v = f × λ where v=velocity, f=frequency, λ=wavelength | Period T = 1/f
- v
- Wave Velocity (m/s)
- f
- Frequency (Hz)
- λ
- Wavelength (m)
Step-by-Step Guide
- 1v = f × λ (wave speed = frequency × wavelength)
- 2f = v ÷ λ (frequency = speed ÷ wavelength)
- 3λ = v ÷ f (wavelength = speed ÷ frequency)
- 4Speed of sound in air (20°C): 343 m/s
Worked Examples
Input
Sound wave, frequency 440 Hz (concert A)
Result
λ = 343 ÷ 440 = 0.780 m (78 cm)
Input
Light, wavelength 550 nm (green)
Result
f = 3×10⁸ ÷ 550×10⁻⁹ = 5.45×10¹⁴ Hz
Frequently Asked Questions
What is the relationship between frequency and wavelength?
Frequency and wavelength are inversely related: higher frequency = shorter wavelength. Together they determine the wave velocity.
What is the speed of light and how does it relate to waves?
Light travels at ≈300,000 km/s (c). All electromagnetic waves travel at this speed, so higher frequency light has shorter wavelengths.
How are sound and light waves different?
Sound is a mechanical wave (requires medium, ≈343 m/s in air). Light is electromagnetic (no medium needed, ≈300,000,000 m/s).
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