Since I do not have your exact document, I will provide a covering the most common advanced wave concepts taught at the A-Level / AP Physics level for Section 13 (often: Standing Waves, Harmonics, and Interference ).
It seems you are asking for to be completed, likely referring to a specific problem set, textbook section, or worksheet (e.g., from AQA, Pearson, Cambridge, or an IB/AP Physics unit). waves 13 complete
[ f_1 = \fracv2L = \frac1202 \times 0.80 = \frac1201.6 = 75 \text Hz ] 3rd harmonic: ( f_3 = 3f_1 = 225 \text Hz ) Problem 2 (Pipe open both ends) A 0.50 m pipe (open both ends) has speed of sound 340 m/s. Find fundamental frequency. Since I do not have your exact document,
[ f_1 = \fracv2L = \frac3401.0 = 340 \text Hz ] Problem 3 (Pipe closed one end) Same length 0.50 m, closed at one end. Find fundamental frequency
[ f_1 = \fracv4L = \frac3404 \times 0.50 = \frac3402.0 = 170 \text Hz ] Next harmonic: ( f_3 = 3f_1 = 510 \text Hz ) (only odd). Problem 4 (Finding wave speed from harmonics) A string fixed at both ends has 3rd harmonic frequency 360 Hz. Length = 0.90 m. Find wave speed.