understanding waves

6.1 UNDERSTANDING WAVES

NURUL FADHILAH ALIAS

http://www.youtube.com/watch?v=OG2eGVt6v2o

http://www.youtube.com/watch?v=eygvPulz4gw&feature=c4-overview&list=UUxmSc1lod8aeZLRhDw_7xQA

http://www.youtube.com/watch?v=Iuv6hY6zsd0MUST SEE

OPTIONAL

CONTENT

• Meaning of wave motion

• Transverse and Longitudinal waves

• Description of water, sound and light waves

• Wavefront (what it is)

• How wavefronts relate to the direction of wave propagation

• Define AmplitudePeriodFrequencyWavelengthWave speed

• Loudness and amplitude

• Pitch and frequency

• Damping

• Resonance

WAVE MOTION

A TYPE OF DISTURBANCE • produced by an oscillating or vibrating motion

in which• A point or body moves back and forth • along a line about a fixed central point

produces waves.

Waves transfer energy without transferring matter

2 types of waves:

• Transverse waves

• Longitudinal waves

TRANSVERSE WAVE

• WAVE in which the vibration of particles in the medium is perpendicular to the

• direction of propagation of the wave

• (water waves, light waves, electromagnetic waves)

Longitudinal waves

• WAVE in which the vibration of particles in the medium is parallel to the direction of

• propagation of the wave

• (sound waves, ultrasound)

WATER

WAV

ES • Low speed

• Transverse• Transmitting

medium is all substances

SO

UN

D W

AV

ES • Higher speed

• Longitudinal• Transmitting

medium is all substances

• The denser the medium the greater the speed

• A LOW FREQUENCY CAUSESA LOW NOTE; A HIGHFREQUENCY, A HIGH NOTE

LIG

HT W

AV

ES • Highest speed

• transverse• Transmitting

medium is all substances EXCEPT opaque object

• The denser the medium the slower the speed

• A LOW FREQUENCY CAUSES RED LIGHT; A HIGHFREQUENCY, VIOLET LIGHT

COMPARING WATER, SOUND & LIGHT WAVES

INTRODUCING…WATER RIPPLE TANK!

Name the sections of the water ripple tank

lampu

Gelombang air

wavefront

Image of wavefront

Skrin putih

penggelek

Tangki riak

To diagram

Diagram shows how the wave fronts are obtained.

Light shining on a ripple tank will cast dark and bright spots on paper/ screen

How wavefronts relate to the direction of wave propagation

Muka gelombang

Arah perambantan

Muka gelombang Arah perambantan

Muka gelombang

Arah perambantan

Rajah (i) Rajah (ii) Rajah (ii)

Merujukkan Rajah (i),(ii) dan (iii), apakah yang boleh dikatakan tentang arah perambatan gelombang dan muka gelombang ?

Jwp.: arah perambatan gelombang sentiasa bersudut tepat kepada muka gelombang.

KNOWING WAVE...

Topic English Bahasa Malaysia

Waves

Wave Gelombang

Wave front Muka gelombang

Propagation Perambatan

Transverse Gelombang melintang

Longitudinal Gelombang membujur

Reflection Pantulan

Activity 1 : Topic and Glossary

Amplitude

Frequency

Longitudinal wave

Period

Wave length

Crest

Trough

Ripple tank

Transverse wave

No Glossaries Meaning

1 Amplitude The maximum displacement from a particle from rest position

2 Frequency The number of complete oscillation per second

3 Longitudinal wave Wave which travels in a direction parallel to the direction of vibration

4 Period Time taken to complete oscillation

5 Wave length The distance between two consecutive crest

6 Crest The maximum point of the wave

7 Trough The minimum point of the wave

8 Ripple tank An instrument to show water wave phenomenon

9 Transverse wave Waves which travel in a direction perpendicular to the direction of vibration

Activity 2 : Glossary – SentenceTopic : Waves

LOUDNESS AND AMPLITUDE

AMPLITUDE: The relative strength of a sound wave, or how much change in pressure occurs.

LOUDNESS: The human perception of amplitude. Depends on the amplitude (or size) of the vibration.

PITCH AND FREQUENCY

The pitch of the sound depends on the frequency of the vibration

DAMPING

DECREASE in the amplitude of an oscillating system is called damping.

(Internal damping: extension and compression of moleculesExternal damping: frictional force/ air resistance)

a ↓ ; f =

RESONANCE

Def. 1: Resonance occurs when a system is made to oscillate at a frequency equivalent to its natural frequency by an external force. The resonating system oscillates at its maximum amplitude.

Def. 2: resonance is the tendency of a system to oscillate with greater amplitude at some frequenciesthan at others. 

Cont. … RESONANCE

natural frequency is the rate at which an object vibrates when it is not disturbed by an outside forceFrequencies at which the response amplitude is a relative maximum are known as the system's resonant frequencies, or resonance frequencies.

Example

At these frequencies, even small periodic driving forces can produce large amplitude oscillations, because the system stores vibrational energy.

Amazing

Resonant

Experiment

!