1.1 Introduction
1.1 Oscillations or Vibrations
1.1 Oscillations or Vibrations some important points
1.1 Wave Quantities
1.1 Wave Properties
1.1 Wave Types
1.1 Speed of Waves
1.1 Simple Harmonic Motion
1.1 Derivation of Period and Frequency for SHM
1.1 Energy in Simple Harmonic Motion
1.1 SHM & Simple Pendulum
1.1 Reflection and Transmission
1.1 Summary
Unit 1.1 Multiple Choice Questions - Waves
Unit 1.1 Multiple Choice Answers - Waves

 

Unit 1.1 Reflection and Transmission of Waves

When a wave strikes an obstacle, or comes to the end of the medium in which it is traveling, at least a part of the wave is reflected. You should be familiar with reflected mechanical waves as in echoes from sounds or water hitting the edges of a swimming pool or the bank of the river or beach.

reflection

— The reflected pulse returns inverted if the end of the cord is fixed. Newton’s third law applies and the support generates the inverted reflected pulse through the application of an equal and opposite force to the upward force of the string.

— The reflected pulse returns right side up if the end of the cord is free. The reflected pulse is generated by the upward force of the forward pulse so it is right side up.

Consider a pulse that travels along a cord which consists of a light section and a heavy section.

— When the wave pulse reaches the boundary between the two sections, part of the pulse is reflected and part is transmitted.

— The heavier the second section of the cord, the less the energy that is transmitted. (When the second section is a wall or rigid support, very little is transmitted and most is reflected)

reflection

— For a sinusoidal wave, the frequency of the transmitted wave does not change across the boundary because the boundary point oscillates at that frequency.

— The transmitted wave has a lower speed (because of the material properties discussed earlier), its wavelength is also less (v = fλ).

— Law of reflection: For reflection of a two or three dimensional plane wave, the angle that the incoming or incident wave makes with the reflecting surface is equal to the angle made by the reflected wave.

reflection

Exercise 1.1.13

1. Describe briefly the behaviour of waves on a string as they move to an end that is (a) unmovable (b) attached to a thicker string (c) free.

 

Concept by Kishore Lal. Programmed by Kishore Lal... Copyright © 2015 Kishore Lal. All rights reserved.