Title 09 Wave Motion Tutorial Solutions.pdf ✅

St. Andrew’s Junior College H2 Physics 9-1 Concept Worksheet Question 1: Displacement-distance graph The graph below shows the shape at a particular instant of part of a transverse wave travelling along a string. State, with a reason, whether the following statements are true or false: (a) The speed of the element at P is a maximum: ................... False. It stops momentarily. (b) The displacement of the element at Q is always zero: ................... False. The instantaneous displacement is zero but it will displace up or down as the wave progresses. (c) The energy of the element at R is entirely kinetic: ................... False. The energy at R is entirely potential energy (d) The energy of the element at S is entirely potential: ................... False. The energy at S is entirely kinetic energy. Question 2: Displacement-time & displacement-distance graphs The graph below shows a displacement-distance graph for a wave containing a particle X that is located 5 m from the source. The wave is travelling rightwards. Given that the period of this wave is 5 s, sketch the displacement-time graph at X: displacement at X time / s
St. Andrew’s Junior College H2 Physics 9-2 Answer: Question 3: Vibrations of transverse wave (Displacement-distance graph) The figure below shows an instantaneous position of a string as a transverse progressive wave travels along it from right to left. Indicate the directions of the velocities of the points 1, 2 and 3 on the string. Question 4: Vibrations of longitudinal wave The diagram on the left shows 13 air particles and their displacements (shown by arrows). Particles A and C are in the regions of compression while particle B is in the region of rarefaction. Taking displacement to the right as positive, draw the displacement-time graph and the corresponding change-in- pressure-time graph. change-in- pressure distance distance displace- ment At t = 0, there is zero displacement at X (as can be seen from displ-distance graph). As time passes, the displacement of particle X increases to a maximum as the crest of the wave passes, falls to zero, continues to a minimum as the trough goes past.
St. Andrew’s Junior College H2 Physics 9-3 Question 5: Phase difference Refer to the displacement-time graph for wave A (bold line) and wave B (dotted) below. [N17/1/14 (mod)] (a) How much (in terms of period, T) is wave A leading wave B by? What is the phase difference in rad? A leads B by 1⁄4 period (or /2 rad). (b) How much (in terms of period, T) is wave B leading wave A by? What is the phase difference in rad? B leads A by 3⁄4 period (or 1.5 rad). Question 6: Relationship between intensity, amplitude and distance from the source A small source of sound radiates energy equally in all directions. At a particular distance r from the source, the intensity of sound is I, corresponding to the amplitude A of oscillation of the air molecules. Write down the relationship between any two quantities in the table below: Quantities Relationship I and r I  1/ r2 I and A I  A2 A and r A  (1/r) Question 7: Polarisation Io, Ao I, A Polarised light of intensity Io and amplitude Ao is shone onto a polaroid. The transmission axis of the polaroid is at an angle  to the vertical. Light emerging from the polaroid has intensity I and amplitude A. Write down equations relating (i) I, Io and , and (ii) A, Ao and . (i) I = Io cos2 θ (Malu’s law) (ii) A = Ao cos θ (resolving vector A into two components)  direction of light polaroid transmission axis