Wave speed from frequency and wavelength Steps:

• Identify period T from one oscillation cycle in Graph 1 (displacement vs. time); frequency f = 1/T.
• Identify wavelength λ as distance between two consecutive crests in Graph 2 (displacement vs. distance).
• Apply wave speed formula v = f λ, using consistent units (cm and s).
• Compute numerical value: if T = 0.01 s (f = 100 Hz) and λ = 3 cm, then v = 100 × 3 = 300 cm/s.

Why D is correct:

• 300 cm/s equals f λ, the standard formula for wave speed in progressive waves.

Why the others are wrong:

• A: 40 cm/s underestimates by confusing period with frequency (e.g., v = λ/T).
• B: 48 cm/s arises from incorrect λ measurement, like half-wavelength.
• C: 150 cm/s halves the frequency, ignoring full cycle in Graph 1.

Final answer: D