01 types of waves (updated 03 dec)

8/13/2019 01 Types of Waves (Updated 03 Dec)

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Waves

Introduction:

Displacement, transverse wave andlongitudinal wave


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Waves : Introduction

What are waves?

Waves are disturbances or vibrations of

particles that transmit energy from a point to

another point. As the waves move further and further away

from the source of vibrations, energy carried

by waves is reducing as it moves further.

Waves travel through a medium; but some

waves can pass through vacuum (eg. Light).


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Waves : Introduction

Are particles travelling as the waves are in

motion?

The motion of particles are revolving or

vibrating about the same point.

What thing is transported by waves? Where

does it come from and pass to?

Energy is transported by waves. It is absorbed

by the waves when external forces causes theparticles to move. It is then passed on to the

next nearest particles.


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Waves : Examples

Sound waves, light waves, radio waves,microwaves, X-ray, infrared and ultraviolet etc..

Sound waves: Produced by vibration of

particles (molecules of substances such as air

or metal).

Electromagnetic waves: Produced by

vibration of electrical charges at different

frequencies.


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Waves : Two basic types

Longitudinal waves

Transverse waves

The displacement of a particle moving in a wave is

measured from the equilibrium position. / rest position.

For transverse wave, the displacement is perpendicular

to the direction of propagation of the wave.

For longitudinal wave, the displacement is parallel to the

direction of propagation of the wave.


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Displacement Displacement is the distance moved by an

object in a specified direction.

It has the same SI unit as distance, which is m.

y

5

10

Suppose a particle vibrates about x axis and the whole x axis

is the rest or equilibrium position.

10

5 x

What is the displacement of the particle?

Ans. +10 units above rest position.

What is the displacement of the particle now?

Ans. 5 units below rest position.

0

For up and down movement; positive displacement means

the particle is above the rest position and negative

displacement means the particle is below the rest position.


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Displacement

y

If the particle vibrates about y axis and the

whole y axis is the rest or equilibrium position.

6

3 x

What is the displacement of the particle?

Ans. +6 units on the right hand side of the rest position.

What is the displacement of the particle now?

Ans.

3 units on the left hand side of the rest position.

0

3 6

For left and right movement; positive displacement means the particle is

on the right hand side of the rest position and negative displacement

means the particle is on the left hand side of the rest position.


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Transverse wave

Motion of waves


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Transverse wave 3 (practice)

Equilibrium

position

1 cm

1 cm

Find the displacement of the black, blue,green and pink particles.

0 cm

5 cm

4 cm

3 cm

Motion of waves

Find the maximum displacement (amplitude) of the wave.

Amplitude of the wave = 6 cm

What is the wavelength?

16 cm

am

plitude

amp

litude


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Longitudinal wave 1

Start


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Longitudinal wave 2

Start


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Longitudinal wave 3: Practice

Motion of waves

Centres of equilibrium positions

Find the displacement of the particles of line1, 4, 6, 7, 9 and 11.

1 2 3 4 5 6 7 8 9 10 11 12

Line 1: 0 cm

2 cm

Line 4: 3 cm

Line 6: 3 cm

Line 7: 4 cm

Line 9: 0 cm

Line 11: 4 cm


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Transverse wave

Amplitude

Amplitude

Peaks or crests

Troughs

Level of medium when it is

at rest (equilibrium position)

Motion of wave


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Longitudinal wave

Areas of compression: This is the areas where

molecules experiences maximum pressure

Areas of rarefaction: This is the areas where

molecules experiences minimum pressure

Motion of wave


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Transverse waveGraph of displacement of particles against distance

displacement / cm

distance / cm

Amplitude

Amplitude


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Transverse waveGraph of displacement of particles against time

displacement / cm

time / s

Amplitude

Amplitude

T: Period


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Longitudinal waveGraph of displacement of particles against distance

displacement / cm

displacement / cm

Amplitude

Amplitude

Centre of

compression

Centre of

rarefaction

Current position

Equilibrium position


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Longitudinal waveGraph of displacement of particles against distance

displacement / cm

displacement / cm

Amplitude

Amplitude

pressure / N/cm2

displacement / cm

01 types of waves (updated 03 dec)

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