1.2 Introduction
1.2 Constructive and Destructive Iinterference
1.2 Phase
1.2 Standing Waves
1.2 Summary
Unit 1.1 Multiple Choice Questions - Waves
Unit 1.1 Multiple Choice Answers - Waves

Unit 2.1 Introduction

In Unit 1, we have examined the properties and behavior of single waves. So now the question arises:

What happens when two waves encounter each other in the same medium?

We are aware that materials experience difficulty sharing space and time. Two objects cannot be in the same space at the same time! Even when one dissolves the other, at the atomic level they are still distinctly occupying 'personal' space and cannot 'violate' each other space! Consequently, in the real world, we use Newton’s laws of motion to determine the movement of a single particle when it experiences an acceleration and thus change its kinetic energy and/or direction of motion. Mechanical waves are observed when forces arise as a result of energy interacting with matter and so these waves really are choreographed dances of particles in the medium. When we see a water wave, for example, energy traverses a medium from a disturbance on the water surface outward in all directions. It is difficult and counter intuitive to see that there is no mass movement of water. As a result, we have to come to terms with the idea that mechanical waves are not material things but energy entities.

Observe that the transverse wave below moves from left to right. On first glance, it may appear that the medium is also moving to the right! But recall that the particles in this transverse wave are moving side to side...

It is probably easier to see this in the animation above where the particles are coloured.

ball ball wave

So now that we have reviewed that waves are really the propagation of energy, we can more specifically, address the question:

What do we observe if two waves propagate in the same space and time?

We have observed waves meeting each other many times! Take, for example, sound waves crisscrossing each other in a room with multiple conversations or water waves resulting from multiple disturbances from the water surface.

At Toco, waves from the Altantic Ocean meet those of the Caribbean Sea in a narrow place between a small island and the mainland. Fishermen and curious onlookers are amazed at the spectacular waves breaking against the nearby Blow-hole rock. These exhibit the effects of two waves of different amplitudes and periods interacting to produce new waves whose amplitude varies with a remarkable periodicity.


We will discuss these ideas in this section.


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