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WAPhysicsQuick questions
Unit 4: Wave Models and Quantum Physics
Quick questions on Standing waves and resonance: WACE Year 12 Physics Unit 4
3short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What are strings fixed at both ends?Show answer
A string fixed at both ends must have a node at each end. The longest wave that fits has a single antinode in the middle, so its wavelength is twice the string length: . Successive harmonics fit more half-wavelengths, giving
What are pipes?Show answer
An open pipe (open at both ends) has an antinode at each end and behaves like the string case, with for all integers . A pipe closed at one end has a node at the closed end and an antinode at the open end, so only odd harmonics exist:
What are counting half-wavelengths?Show answer
To find a harmonic, sketch the pattern, count nodes and antinodes against the boundary conditions, and read off how many half-wavelengths fit the length. Mislabelling an open pipe as closed (or vice versa) changes which harmonics exist, so identify the ends first.
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