Wave speed determines wavelength for fixed frequency Steps:

• Frequency f is the same for both string and air waves from the same source.
• Use v = f λ to find λ_string = 400 / f and λ_air = 340 / f, so λ_string > λ_air.
• Plot f vs λ: each follows f = v / λ, a decreasing curve; string's curve lies above air's (higher v yields higher f for same λ).
• Graph C shows two inverse curves with string above air, matching v_string > v_air.

Why C is correct:

• Matches v = f λ, where same f and higher v_string produce steeper inverse relation.

Why the others are wrong:

• A shows direct proportion, violating v = f λ.
• B swaps curves, implying v_air > v_string.
• D shows identical curves, ignoring speed difference.

Final answer: C