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 Wave Properties

The properties of waves

 wave propertiesSuppose that two people are holding opposite ends of a taut rope.

— Suddenly one person snaps the rope up and down quickly once.

— That “disturbs” the rope and puts a hump in it which travels along the rope toward the other person.

— The traveling disturbance is one kind of a wave, called a pulse.

— Originally, the height above ground of each point on the rope depended only upon its position along the rope as the rope was motionless.

— When the rope was snapped, a rapid change is created in the height of the left end.

— Each point oscillates down, back to the initial position, up and back to the initial position, as the pulse passes. The height of each point on the rope now depends also upon time.

The disturbance is a pattern of displacement moving along the rope.

— A wave is created by the motion of the displacement pattern along the rope.

— The hand snapping one end is the source of the wave.

— The rope is the medium in which the wave moves.

Another example.

A stone falling into a pool of still water creates a series of circular crests and troughs spreads over the surface.

— This moving displacement pattern (crests and troughs) of the liquid surface is a continuous or periodic wave.

— The pebble disturbing the surface is the source.

— The liquid surface is the medium. Objects floating on the surface of the liquid bob up and down as each wave passes. But they do not experience any sideways displacement on the average. Material has NOT moved from the wave source along with the wave, either on the surface or among the particles of the liquid

— Only the energy and momentum contained in the disturbance have been transmitted. The same holds for all mechanical waves like string waves, sound waves in air, etc.

 

Summary:

— A disturbance in a medium results in a pulse when particles are moved from their equilibrium position to one side, returned to the equilibrium position.

— A wave is created by the motion of the displacement pattern along the rope.

— The object which creates the disturbance is the source of the wave.

— Mechanical waves must have a medium to propagate.

— No material travels with the wave in the medium or is permanently displaced.

— Only energy and momentum travel with the wave.

— Some waves like string waves and water waves are easy to see but others like pressure or electric field cannot be detected by the naked eye!

wave properties

wave properties

wave properties

wave properties

wave properties

Oscillations or Vibrations – Thinking about the concept!

 wave propertiesHave you ever played ‘catch’ at the beach and missed the ball only to see it floating in the ‘smooth waves’ (not the breakers) out of reach? Intuitively we expect the ball to be washed out to the beach (towards us), but is that the experience?

 

Facts!

— The wave moves with a fairly fast speed towards the beach!

—The balls actually moves up and down!

 

Questions…

But how are the particles in the water moving?

Are they moving towards the beach with the wave?

Does the ball give any indication of how the water particles are moving? Concepts…

 

Exercise 1.1.5:

Make a statement on the Velocity of Wave vs. Particle Make a statement on the Energy of the Wave vs. Particle.

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