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QLDPhysicsQuick questions

Unit 2: Linear motion and waves

Quick questions on Waves and sound: QCE Physics Unit 2 Year 11

12short 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 is amplitude?
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maximum displacement from equilibrium. Determines energy.
What is transverse?
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Oscillation perpendicular to propagation direction. Examples: light, water surface, transverse waves on a string.
What is longitudinal?
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Oscillation parallel to propagation. Compressions and rarefactions. Examples: sound, P waves in earthquakes.
What is reflection?
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Wave bounces off boundary. Angle of incidence = angle of reflection.
What is refraction?
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Wave changes direction at boundary between media (different speeds).
What is diffraction?
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Wave bends around obstacles or through openings. Greater when wavelength comparable to opening.
What is interference?
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Two waves superpose: constructive (in phase) and destructive (out of phase).
What is polarisation?
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Only transverse waves. Light passing through polariser: I=I0cos⁡2θI = I_0 \cos^2 \theta (Malus's law).
What is doppler direction?
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Approaching: higher frequency. Receding: lower.
What is q1?
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State the electromagnetic spectrum in order of increasing frequency. [2 marks]
What is q2?
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A source emits 440 Hz440 \text{ Hz} and moves toward an observer at 20 m s−120 \text{ m s}^{-1} (vsound=340 m s−1v_{sound} = 340 \text{ m s}^{-1}). Calculate the observed frequency. [3 marks]
What is q3?
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A Brisbane River ferry horn at 200 Hz200 \text{ Hz} approaches a stationary listener at 30 m s−130 \text{ m s}^{-1} (vsound=340 m s−1v_{sound} = 340 \text{ m s}^{-1}). (a) Calculate the observed frequency. (b) Calculate the wavelength in front of the moving ferry.

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