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SMSains Muzaffar Syah

What is A Transverse Wave?

A transverse wave is a wave in which thevibration of particles in the medium isperpendicular to the direction ofpropagation of the wave.

Example: water waves, light waves,electromagnetic waves

What is Longitudinal Waves?

A longitudinal wave is a wave which thevibration of particles in the medium isparallel to the direction of propagation ofthe wave.The slinky spring moves backwards andforwards to produce a longitudinal wave.The particles of the medium (spring) mparallel to the direction of the wave. Thewave that travels along the spring consistsof a series of compression and rarefraction

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What iswaves?

Process of transferringproduced by an

How dowavestransferenergy?

When energy is transferred by a wave from a vibrating source to a distantreceiver, there is no

When a stone is dropped into a pond, The direction of propagation of the water waves is f The cork represents the The cork does not move together with the wave, instead it moves

down about its initial position. Waves transfer

However, the waves do not carry the

This shows that wave transferring energy without transferring matter.

is a wave in which thein the medium is

to the direction of

water waves, light waves,

is a wave which thein the medium is

direction of propagation of

The slinky spring moves backwards andforwards to produce a longitudinal wave.The particles of the medium (spring) move

to the direction of the wave. Thewave that travels along the spring consists

rarefraction.

Process of transferring energy from one location to another which isproduced by an oscillating or vibrating motion.

When energy is transferred by a wave from a vibrating source to a distantreceiver, there is no transfer of matter between the two points.When a stone is dropped into a pond, water waves are produced.The direction of propagation of the water waves is from leftThe cork represents the water particles.The cork does not move together with the wave, instead it moves

about its initial position.Waves transfer energy as they move along the water particles.However, the waves do not carry the water particles along with them.


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from one location to another which is

When energy is transferred by a wave from a vibrating source to a distantof matter between the two points.

waves are produced.left to right.

The cork does not move together with the wave, instead it moves up and

as they move along the water particles.particles along with them.



Activity 1: To observe a longitudinal wave and a transverse wave using a slinky spring.

1. Hold one end of a slinky spring and give a sharp push at the other end of the springand forward. Observe the movement of the spring.

(a) Sketch the longitudinal wave produce by the slinky spring.

(b) Label the parts of compressionwave produced.

(c) Show the direction of the vibration of the coloured thread and the direction of propagationof the wave (movement of the spring.

(d) The coloured thread which represents a ppropagation of the wave.

(e) The wave that travels along the spring consists of a series ofrarefraction.

(f) The wavelength is the distance between twocompression

2. Use the same slinky spring move the other end of the spring side ways. Observe themovement of the spring.(a) Sketch the transverse wave produced by the slinky spring.

(b) Label the wavelength of the wave produced.(c) Show the direction of the vibration of the coloured thre

of the wave (movement of the spring.

To observe a longitudinal wave and a transverse wave using a slinky spring.

slinky spring and give a sharp push at the other end of the spring. Observe the movement of the spring.

Sketch the longitudinal wave produce by the slinky spring.

compression and rarefaction of the spring and the wavelength

Show the direction of the vibration of the coloured thread and the direction of propagationof the wave (movement of the spring.

red thread which represents a particle of the medium vibrate parallel

The wave that travels along the spring consists of a series of compression

is the distance between two successive rarefraction or two

slinky spring move the other end of the spring side ways. Observe the

Sketch the transverse wave produced by the slinky spring.

Label the wavelength of the wave produced.Show the direction of the vibration of the coloured thread and the direction of propagationof the wave (movement of the spring.

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To observe a longitudinal wave and a transverse wave using a slinky spring.

slinky spring and give a sharp push at the other end of the spring backward

wavelength of the

Show the direction of the vibration of the coloured thread and the direction of propagation

parallel to the

compression and

or two successive

slinky spring move the other end of the spring side ways. Observe the

ad and the direction of propagation


(d) The vibration of the coloured thread isthe wave.

ConclusionA longitudinal wave is a wave in which the vibration of the medium isthe propagation of wave.A transverse wave is produced when the vibration of the medium isof the propagation of wave.

What is a ripple tank?

The phenomenon of water waves can be investigatedusing a ripple tank.The water waves are produced by athe water surface.

The tank is leveled so that the depthtank is uniform to ensure water waves propagate withconstant speed.

How the dark and bright bands are formed on thescreen?

The water acts as a lens to produce a pattern ofand bright regions on a piece of white paper placedunder the tank when light passes through it.

Water waves have crests and troughs.

A crest is the highest position of the wave acts as aconvex lens, whereas a trough is the lowest positionacts as a concave lens.

Light rays from the lamp on top will focus onto thewhite screen below. The bright lines correspond to thecrests, and the dark lines correspond to the troughs.

The vibration of the coloured thread is perpendicular to the direction of the propagation of

A longitudinal wave is a wave in which the vibration of the medium is parallel to the direction of

A transverse wave is produced when the vibration of the medium is perpendicular

The phenomenon of water waves can be investigated

The water waves are produced by a wooden bar on

depth of water in thetank is uniform to ensure water waves propagate with

How the dark and bright bands are formed on the

to produce a pattern of darkregions on a piece of white paper placed

under the tank when light passes through it.

Water waves have crests and troughs.

A crest is the highest position of the wave acts as alens, whereas a trough is the lowest position

Light rays from the lamp on top will focus onto thelines correspond to the

lines correspond to the troughs.

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to the direction of the propagation of

to the direction of

perpendicular to the direction


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What is meant by a wavefront?

Lines joining all the points of the same phase are calledwavefronts.

The wavefronts of a transverse wave and longitudinalwave are perpendicular to the direction of propagationof the waves.

Two types of wavefronts:

1. circular wavefronts 2. plane wavefronts

Describing Waves

Vibration/Oscillation : The movement from one extreme position to the other and back to the sameposition.

Amplitdue, a : The maximum displacement from its equilibrium position. SI unit: meter, m

Period, T : The time taken for an oscillation to complete one cycle. SI unit is second (s)

Frequency, f : The number of waves produced in one second. SI unit is Hertz (Hz)

Wavelength , λ: The distance between two successive crests or two successive troughs or the

distance between two successive compressions or two successive rarefactions in

a sound wave.

Velocity, v :The measurement of how fast a crest is moving from a fixed point. SI unit is ms-1

.


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Displacement-time graph and Displacement-distance graph for a wave.The motion of an oscillating spring can be plotted on a displacement against time graph.

O is called the equilibrium position. a is the amplitude. T is the period of the oscillation.

Displacement against distance graph

Displacement of a particle against distance measured along the wave

a = amplitude. λ = wavelength

Relationship between frequency and wavelength

At constant speed, when the frequency increases, the wavelength willdecrease. Frequency is inversely proportional to wavelength.


The relationship between speed, wavelength and frequency

Speed = distancetime

For one complete oscillation, the distance traveled is the wavelength of the wave. The time takento travel such distance is period. So,

Speed = wavelengthPeriod

Since period = 1 __ .Frequency , therefore speed =

Exersise 1

1. (a) The wavelength of the wave in the diagram above is given by letter

(b) The amplitude of the wave in the diagram above is given by letter

2. Indicate the interval which represents one full wavelength.

Answer: ABCDE, C-G, B-F

2. What is the frequency of water waves with the wavelength of 4.0 cm andof 1.6 cm s

-1?

The relationship between speed, wavelength and frequency

For one complete oscillation, the distance traveled is the wavelength of the wave. The time takento travel such distance is period. So,

, therefore speed = frequency x wavelength

1. (a) The wavelength of the wave in the diagram above is given by letter A

(b) The amplitude of the wave in the diagram above is given by letter D

2. Indicate the interval which represents one full wavelength.

What is the frequency of water waves with the wavelength of 4.0 cm and traveling at a speed

v = fλ

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For one complete oscillation, the distance traveled is the wavelength of the wave. The time taken

traveling at a speed


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3. Measure the wavelength and calculate the speed of the wave. The frequency of the wave is 50Hz.

Λ = 2 cmv = (50) (2)

= 100 cm s-1

= 1 m s-1

4. If the speed of light is 3.0 x 108

m s-1

, what is the frequency of light with the wavelength of 8.0x 10

-7m?f = v/λ = 3.0 x 10

8/ 8.0 x 10

8= 0.375 Hz

5. From the graph, calculate:

(a) AmplitudeA = 10 cm

(b) PeriodT = 0.4 s

(c) frequency

f = 1/T = 1/0.4 = 2.5 Hz

6. A graph shows a wave produce by aslinky spring vibrating at frequency 8Hz. What is:

(a) amplitudeA = 10 cm

(b) wavelength

λ = 1.0 cm

(c) wave speed

v = fλ = 8 x 1.0 = 8.0 cm s-1

7. Which of the graphs has a higher frequency?

A B


Damping in an Oscillating System

What isdamping?

Damping is the decreaseenergy is lost asThe amplitude of an oscillating system will gradually decrease and becomewhen the oscillation stops.

What causesdamping?

1. External dampingforces or air resistance.

2. Internal dampingof the molecules in the system.

Sketch agraph toshowdamping

Resonance in an oscillating system

ExternalForce

Forceoscillation

Naturalfrequency

Resonance

To enable an oscillating system to go onbe applied to the system.

The external force suppliesforced oscillation

The frequency of a system which oscillates freely without the action of anexternal force

Resonance occurs when a system is made toequivalent to itssystem oscillates at its

Activity 2: Damping effect in a vibrating system1. Set up the apparatus as shown below.2. Fix a saw blade horizontally on the leg

of a laboratory bench using a G3. At the other end of the blade, fix a piece

of plasticine (50 g)4. Move the plasticine to the position X

and release it.5. Observe the position Y reached by the

plasticine.6. Observe subsequent Y positions of the

plasticine.

Damping in an Oscillating System

decrease in the amplitude of an oscillating system when itsenergy is lost as heat energy.The amplitude of an oscillating system will gradually decrease and becomewhen the oscillation stops.

External damping of the system is the loss of energy to overcomeor air resistance.

Internal damping is the loss of energy due to the compressionof the molecules in the system.

Resonance in an oscillating system

To enable an oscillating system to go on continuously, an external force mustbe applied to the system.

The external force supplies energy to the system. Such a motion is called aforced oscillation

cy of a system which oscillates freely without the action of anforce.

occurs when a system is made to oscillate at a frequencyto its natural frequency by an external force. The resonating

system oscillates at its maximum amplitude.

Activity 2: Damping effect in a vibrating systemSet up the apparatus as shown below.Fix a saw blade horizontally on the legof a laboratory bench using a G-clamp.At the other end of the blade, fix a piece

plasticine to the position X

Observe the position Y reached by the

Observe subsequent Y positions of the

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of an oscillating system when its

The amplitude of an oscillating system will gradually decrease and become zero

to overcome frictional

compression and extension

an external force must

to the system. Such a motion is called a

cy of a system which oscillates freely without the action of an

frequencyThe resonating


Observation:What changes do you observe in the position Yover several oscillations?

Conclusion:The position Y becomes …………………(fartherplasticine oscillates.

Discussion1. Why does the spring oscillate closer

and closer to the equilibrium2. What happens to the energy possessed

by the plasticine and the blade?

3. What happens to the oscillation of theblade after a long time?

4. What is the name given to thisphenomenon?

5. How do you overcome the dampingeffect of the oscillation

6. A mother puts her baby to sleep in asarong cradle. She needs tocontinuously move the sarong cradleup and down.

What changes do you observe in the position Y The position Y becomes closer over severaloscillations

The position Y becomes …………………(farther / closer) to the equilibrium position each time the

Why does the spring oscillate closerand closer to the equilibrium position?

Its amplitude decreases.

What happens to the energy possessedby the plasticine and the blade? Energy possess decreases and lost to heat.

What happens to the oscillation of theIt will stop.

to thisDamping

How do you overcome the dampingGive external force or push the plasticine ball.

A mother puts her baby to sleep in asarong cradle. She needs tocontinuously move the sarong cradle

(a) What happen to the sarong cradle whenthe mother stops moving the cradle upand down?

Amplitude decreases

(b) Suggest a reason for the movement ofthe sarong cradle discussed in (a).

Damping, lost energy to heat

(c) What must you do if you want to help themother to maintain the movement of thecradle?

Move the cradle up and down / giveexternal force

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becomes closer over several

) to the equilibrium position each time the

Energy possess decreases and lost to heat.

Give external force or push the plasticine ball.

What happen to the sarong cradle whenthe mother stops moving the cradle up

Suggest a reason for the movement ofthe sarong cradle discussed in (a).

Damping, lost energy to heat

What must you do if you want to help themother to maintain the movement of the

Move the cradle up and down / give


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Experiment inBarton’spendulum

How doesresonanceoccur in thetwopendulum ofequal length?

The frequency of a simple pendulum depends on the length of the pendulum.

In Barton’s pendulum experiment, there are many pendulums tied to the rope.Two of the pendulum are of the same length

When pendulum B oscillates, all the other pendulums are forced to oscillate.

But pendulum D oscillates with the largest amplitude, ie, pendulum Dresonates

Pendulum B and pendulum D are of the same length.

Frequency B equal Frequency D

Therefore, pendulum B causes pendulum D to oscillate at its naturalfrequency.

Good effectsof resonance

Explain how the tuner in a radio enables us to select the programs we areinterested. The circuit in the tuner is adjusted until frequency of the radio waves

produced in the radio is equal to the frequency transmitted by a particularstation. Resonance is achieved. The frequency transmitted by a particularstation will be selected. Hence a strong electrical signal is produced.

How does aguitar work? When the guitar string is plucked, the string will

start to vibrate and produce distinct sounds.The guitar string is attached to the sound box ofthe guitar.The vibrating string forces air particles inside thebox to vibrate at the same natural frequency as the string.The sound box vibrates with the string and sets more air particles to vibrate thusproducing loud sound.

Bad effects ofresonance

Explain how the Tacoma Bridge collapsed. The movement of the wind might have the same frequency as the natural

frequency of the vibration of the bridge. As a result, resonance occured The action of the wind caused the bridge to vibrate with a large amplitude

and it collapse.

SM Sains Muzaffar Syah

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