1.1 understanding waves.ppt

Chapter 1 WavesChapter 1 WavesChapter 1 WavesChapter 1 Waves

2.1 Arah Mata Angin1.1 Understanding Waves

Understanding WavesChapter 1 Waves

Waves

The Nature Of Waves

Travelling disturbance through a medium from a vibrating or oscillating source

Medium

Transfers energy in the direction of its propagation but do not transfers matter.

• The medium is a substance or material that transports the wave from its source to another place

• The particles to the medium only vibrate but do not travel together with the wave

Chapter 1 Waves

Jenis gelombang

Gelombang melintang Gelombang membujur

Zarah medium bergetarpd arah yg berserenjangdengan arah perambatan gelombang

Zarah mediumbergetarpd arah yg selaridengan arah perambatan gelombang

contoh

air

Elektromagnetik

contoh

bunyi


Wavefront

• An imaginary line that joins all the points on the points on the crest of a wave

• The direction of wavefront is perpendicular to the direction ot the propagation of its wave

Circular wavefronts Plane wavefronts


Oscillating System

An oscillating system is a system that undergoes a periodic to-and-fro movement

Examples A simple pendulum A loaded spring

Amplitude, A = maximum displacement form its rest position (meter, m)Period, T = time for one complete oscillation / vibration (second, s)

Frequency, f = number of complete oscillation / vibration in one second (Hertz, Hz)Wavelength, = distance between two successive crests (meter, m)Wave speed, v = distance moved by a wave in one second (meter per second, ms-1)

R PQ

A A

P – Q – R – Q – P


Example :

In an experiment, siti observes that a simple pendulum completes 40 oscillation in 48.0 seconds. What is a) the period of oscillation b) the frequency of oscillation


Displacement-Time Graph

A

A

T

T

A = amplitude T = Period


0.02 0.04 0.06

ExampleFigure below shows the displacement –time graph of the oscillating of mass on a springFrom the graph statea)Amplitudeb)Periodc)frequency

5

-5


Displacement-Distance Graph

A

A

A = amplitude T = Period


3.7 7.4 11.1

ExampleFigure below shows the displacement –distance graph ofA waveFrom the graph finda)Amplitudeb)Wavelength of the wave

8

-8

distance


Speed Of Waves

v = f v = wave speed

f = wave frequency

= wavelength

The frequency of a wave moving to the shore is 6 Hz and the length between two waves trough is 3m. What is the speed of the wave?

v = f = 6 × 3

= 18 ms-1

Example 1


Speed Of Waves

Example 2

A teacher attaches a slinky to the wall and begins introducing pulses with different amplitudes. Which of the two pulses (A or B) below will travel from the hand to the wall in the least amount of time?

AnswerBoth of the pulses reach the wall at the same time because the amplitude of the wave does not affect the speed of the wave.


Damping In An Oscillating System

No energy loss (the system oscillates forever)

Oscillating System In Vacuum

Amplitude decreases

Oscillating System In The Air

Energy loss to the surroundings due to air resistance and friction

Damping is said to have occurred in an oscillating system when there is a loss of energy to the surroundings.

Since the length of the pendulum B string = length of the pendulum string E, both pendulums B and E have the same natural frequency.Therefore, pendulum E is at resonance with pendulum B and will oscillate with larger amplitude.


Resonance

An oscillating system is at resonance when it is driven at its natural frequency by a periodic force.

At resonance, the amplitude of the ascillating system rises to maxiumum.

Barton’s Pendulum


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1.1 Understanding Waves1.1 Understanding Waves

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1.1 Understanding Waves1.1 Understanding Waves

1.1 understanding waves.ppt

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