Speed of sound from closed-tube harmonic relation Steps: - The setup has two antinodes and two nodes, indicating the third harmonic (odd mode) in a tube closed at one end, where 3λ/4 = L. - Rearrange to λ = 4L/3, so frequency f = v/λ = 3v/(4L), or v = 4fL/3. - The graph shows f inversely proportional to L (hyperbolic decrease), confirming the relation; convert L from cm to m. - Select a graph point, e.g., at L ≈ 10 cm (0.1 m), f ≈ 2250 Hz, yielding v = (4 × 2250 × 0.1)/3 = 300 m/s. Why C is correct: - v = 300 m/s matches the calculated speed from f = 3v/(4L) using graph data, per the wavelength formula for closed-pipe harmonics. Why the others are wrong: - A: 150 m/s underestimates v, yielding f ≈ 1125 Hz at L = 0.1 m, below graph values. - B: 250 m/s gives f ≈ 1875 Hz at L = 0.1 m, inconsistent with observed frequencies. - D: 400 m/s overestimates v, yielding f ≈ 3000 Hz at …