Speed of sound in gases, liquids and solids
Wave motion · Physics
Transverse wave
Interactive 3DA travelling wave ribbon. Raise the amplitude to make it taller, the frequency to make it faster.
Controls
Drag the sliders or type a value — the simulation updates live.
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0.1m1m
Hz
0.5Hz3Hz
Study notes
Compare the speed of sound in (a) air at 20°C and (b) helium at 20°C. (M_air = 29 g/mol, M_He = 4 g/mol, γ_air = 1.4, γ_He = 1.66, R = 8.314 J/mol·K) Step 1: v = √(γRT/M), T = 293 K. For air: v = √(1.4 × 8.314 × 293 / 0.029) = √(117,600) ≈ 343 m/s. Step 2: For helium: v = √(1.66 × 8.314 × 293 / 0.004) = √(1,011,000) ≈ 1005 m/s. Step 3: Ratio ≈ 1005/343 ≈ 2.93. Answer: (a) ≈ 343 m/s, (b) ≈ 1005 m/s — nearly 3× faster, mostly because helium is ~7× lighter. That's the physics behind the squeaky helium voice.