8/18/2019 1.1 waves.PPT

1/21

1

1.1 Waves

8/18/2019 1.1 waves.PPT

2/21

2

Motion of Waves

 A boy is moving to and fro on a swing.

This type of motion is called an oscill

ation.

8/18/2019 1.1 waves.PPT

3/21

3

Motion of Waves  An oscillating or vibrating motion in which a

point or body moves back and forth along a lineabout a fixed central point produces waves.

Examples: Light waves are produced as a result of

 vibrations of electrons in an atom.

Sound waves are produced by vibrating

mechanical bodies such as guitar strings or atuning fork.

 Water waves are produced by a distur

 banceon a still water surface.

8/18/2019 1.1 waves.PPT

4/21

4

Motion of Waves Waves are carrier of energy .

They transfer energy from onelocation to another.

 Waves transfer energy withouttransferring matter.

8/18/2019 1.1 waves.PPT

5/21

5

Motion of Waves

The waves transfer energy from the stoneto the cork.

The cork does not moves outwards as the

 wave passes because the water itself doesnot move outwards.

Conclusion: Energy is transferred from stone to the cork

 which does not involved the transfer of wat

er.

8/18/2019 1.1 waves.PPT

6/21

6

 Transverse Waves

 A transverse wave is one in which the

 vibration of the medium is perpendi

cular to the direction of propagation of the wave.

Examples: water waves light waveselectromagnetic waves.

8/18/2019 1.1 waves.PPT

7/21

8/18/2019 1.1 waves.PPT

8/21

8

Dierences

8/18/2019 1.1 waves.PPT

9/21

9

Wave fronts

 Water wave have crests and troughs.

 A crest is the highest position of the wave.  A trough is the lowest position of the wave.

"n waves lines #oining all the points ofthe same phase are called wave fronts.

8/18/2019 1.1 waves.PPT

10/21

10

Wavelengths (λ)

The wavelength of a wave is the distance between two ad#acent points of the same

phase on a wave.

$" unit: m

8/18/2019 1.1 waves.PPT

11/21

11

Amplitude (a)

The amplitude of a wave is its maximumdisplacement from its e%uilibrium position.

$" unit: m

8/18/2019 1.1 waves.PPT

12/21

12

Period (T) !re"uenc# (f)

The period of a wave is the time takenfor an oscillation to complete one cycle.

$" unit: s The fre%uency of a wave is the number

of waves produced by a source in oneunit time.

$" unit: &' s()

T   =1

f 

8/18/2019 1.1 waves.PPT

13/21

13

Wave $peed (v) The speed of a wave is the

measurement of how fast a crest ismoving from a fixed point.

$" unit: ms()

 v = f

8/18/2019 1.1 waves.PPT

14/21

14

Displacement%Time

&raph

8/18/2019 1.1 waves.PPT

15/21

15

Displacement%Distance &raph

8/18/2019 1.1 waves.PPT

16/21

16

'ample 1

8/18/2019 1.1 waves.PPT

17/21

17

'ample

8/18/2019 1.1 waves.PPT

18/21

18

"n an oscillating system such as the oscillationof a simple pendulum the oscillation does notcontinue with the same amplitude indefinitely

except when the system is oscillating in vacuum.

The amplitude of oscillation of the simplependulum will gradually decreases and

 become 'ero when the oscillations stops. The decrease in the amplitude of an

oscillating system is called damping.

Damping

8/18/2019 1.1 waves.PPT

19/21

19

Damping

8/18/2019 1.1 waves.PPT

20/21

20

To enable an oscillating system to go oncontinuously an external force must be

applied to the system. The external force supplies energy to the

system. $uch a motion is called a forcedoscillation.

The fre%uency of a system which oscillatesfreely without the action of an external force iscalled the natural frequency .

Damping

8/18/2019 1.1 waves.PPT

21/21

21

*esonance occurs when a system ismade to oscillate at a frequency

equivalent to its natural frequency   by an external force.

The resonating system oscillates at its

maximum amplitude.

*esonance