Title Bk3-TE15-Interference-and-Stationary-Waves.pdf ✅

Superposition 79 15.1 Fig. 15.2 shows the typical results when two pulses meet. When two crests meet, they add up to a larger crest. When a crest meets a trough, a smaller crest or trough is formed. They may even cancel out each other if they have exactly inverted shapes. In any cases, two pulses can pass straight through each other without changing each other’s shape. This phenomenon is called superposition. All waves exhibit superposition. B Principle of superposition In fact, the addition of pulses or waves obeys the principle of superposition. 1. When two waves meet, the resultant displacement is the vector sum of the two displacements. 2. Aft er the waves separate, they travel in their original directions, as if nothing has happened. (a) Two pulses form a pulse of a larger amplitude. (b) Two pulses form a pulse of a smaller amplitude. (c) Two pulses cancel out each other. Fig. 15.2 Superposition of pulses Simulation Principle of superposition Teaching notes Emphasize that it is the resultant displacement of the particle being the sum of the displacement of the two waves but not the amplitude. The resultant displacement is not the sum of the amplitudes! superposition 疊加 principle of superposition 疊加原理 M03_APHY_SB_03HKG_7376_C15.indd 79 15年7月7日 下午7:32 For inspection © United Prime Educational Publishing (HK) Limited, Pearson Education Asia Limited 2023 All rights reserved; no part of this publication may be reproduced, photocopied, recorded or otherwise, without the prior written permission of the Publishers.