Waves

Waves

Knowledge :

1. Any motion that repeats itself in equal intervals of time is called a periodic motion.

2. If a particle in a periodic motion moves back and forth over the same path, we call the motion oscillatory or vibratory.

3. Some examples of periodic motion are the oscillation of the balance wheel of watch, a violin string, a mass attached to a spring, a simple pendulum , a vibrating saw blade and air molecules as a sound wave passes by.

4. Wave motion is due the ________________ of particles from their rest position.5. Several terms to describe a wave:

a. Wavelength ( ( ) , the _______________ between two adjacent points of the same phase on a wave.

b. Amplitude ( a ) , is the maximum _____________________ of a crest or a trough from the equilibrium position

c. Frequency ( f ) , is the _______ of waves produced by a source in one unit time.

d. Wave speed ( v ) , is the measurement of __________ ____________ a crest is moving from a fixed point

e. Period ( T ) , is the ____________ taken for an oscillation to complete one cycle6. Waves are _____________ of energy. They ________________ energy from one location to another. The energy is represent by the amplitude of the wave.

Example :

When we throw a stone into a pond, a ripple spreads out in an expanding circle from the source of disturbance. The energy of the stone is converted to waves. A cork floating a distance away will move up and down when the ripples passes it. Thus the ripple transfer energy from the stone to the cork

7. There are many examples of waves such as microwaves, radio waves, sound waves. These waves are divided into ________________and ______________ waves.a. Transverse waveThe direction of propagation of the wave formed is _______________ to the vibration of the medium

Example :

b. Longitudinal waves

Waves where the vibration of the medium is ________________ to the direction of propagation of the wave

8. Examples of transverse waves are water waves, radio waves, microwaves and etc. While sound waves is a longitudinal waves.

9. The relationship between f and T is or

T is inversely proportional to f If T increase, f will decrease and vice versa .

The unit of T is second while f is Hz @ s -110. The swing of a simple pendulum is always used to illustrate some of terms waves.

The maximum displacement is called amplitude ( a )

The time to swing from position A to B and back to A is called a period ( T ).

T simple pendulum where l = length of the pendulum and g = 10ms-1 Frequency is defined as the number of complete swings of the pendulum bob from A to B and back from B to A per unit time ,

When the bob is displaced to one side, the bob will gain potential energy, Ep where :

Ep = gravitational potential energy m = mass of the bob g = gravitational field strength ( 10 ms -2 ) ( round off to tens ) h = maximum displacement from its equilibrium position and when the bob is released to let it oscillates , the potential energy will transform to

kinetic energy , Ek , where

m = mass of the bob v = the speed of oscillation .

11. Many of oscillating bodies do not move back and forth between precisely fixed limit. The bob will stop after a long period of time. We call this phenomenon as _______________. Damping is caused by frictional force dissipate the energy of the motion.12. Waves has speed. For example, the speed of sound waves is about 330 ms-1 and the speed of light is 3.0 x 108 ms-1. The _________ of wave can be determine by

v = the speed of a wave f = the frequency of wave = the wavelength of a wave ( lamda )

13. We can see a wave in lab using a ripple tank.

14. A ripple tank consists of a square transparent plastic tray with a lamp on the top. The tray has sloping sides so that any wave propagate will not be reflected back from the side

15. Two patterns of wavefronts are :

16. Water waves have crests and troughs. A crest is the highest position of the wave, whereas a trough is the lowest position. The crest act as a ___________ lens while the trough act as a ___________________ lens. 17. In a ripple tank, light rays from the lamp on top will focus onto the white screen below. The bright lines correspond to the _______, and the dark line correspond to the _______.

Figure to show how wavefronts are formed

18. Displacement distance graph

19. Displacement time graph

Example 1 :

Figures below shows the displacement-distance graph and displacement-time graph of a

wave travelling from left to right.

Determine :

a.The amplitude, a

..

b.The wavelength , (

..

c.The period , T

..

d.The frequency , f

.

e.The speed , v , of the wave

.Example 2

Figure shows a long spring along which a longitudinal wave is moving

a. What is meant by longitudinal wave?

__________________________________________________________________________________________________________________________________b. Mark on the diagram

i. With a letter C which represent a point of compression

ii. With a letter R which represent a point of rarefaction

iii. Mark on the diagram a distance equal to the wavelength of the wave and label this distance as (c. Give an example of a longitudinal wave

_________________________________________________________________

Example 3

Figure below shows water waves being generated by a linear dipper oscillating in a ripple

tank with a deep area and a shallow area.

a. State two changes when the wave enters the shallow are

1. _______________________________________________________________2. _______________________________________________________________b. If the frequency of the oscillating linear dipper is 5 Hz, the wavelength of the waves in the deep area is 4.0 cm and the wavelength of the waves in the shallow area is 3.0 cm, calculate :

i. the speed of the waves in the deep area

_________________________________________________________________

ii.the speed of the waves in the shallow area

_________________________________________________________________

Example 4

Each line in the diagram below is a crest line

The wave travels from X to Y in 2 s. What is the frequency of the wave?

Answer : ______________________________________________________________

Example 5

The diagram shows a wavefront pattern produced by a dipper vibrating at a frequency of

12 Hz in a ripple tank

What is the speed of the waves

Answer : ________________________________________________________________

20. If a periodic force is applied to a swing as its natural frequency, the amplitude of the swing increases as the energy of the swing increases. The swing is said to be in resonance.

21. At resonance the swing oscillates with a maximum amplitude.Reflection of waves

Example 1

The diagram shows a light ray reflected on a plane mirror

What is the angle of incidence of the light ray?

Answer : ________________________________________________________________Refraction of waves

Example 1

Complete the diagram below to show refraction when a plane water wave is passing through a shallow area

Example 2

The diagram shows a plane water wave in a ripple tank moving across a convex transparent block. Complete the diagram to show refraction when the plane water wave is passing through the convex shallow area

Example 3

Complete the diagram below to show refraction when a plane water wave is passing through a concave shallow area

Diffraction of waves1. Diffraction of waves is a phenomenon when a wave is pass through an _____________or around an _____________________________2. v, f dan are _____________ __________________ in diffraction

3. The amount of diffraction ( the sharpness of the bending ) ______________ with increasing wavelength

4. In fact, when the wavelength of the waves is smaller than the width of the obstacles, there is less noticeable diffractionExample 1

Example 2

Interference of waves1. Interference is a phenomenon when two waves ____ while travelling along the same medium

2. Ripples riding higher on the surface of the sea near a boat. Water waves move towards the side of the boat and are reflected back. The incident waves and the reflected waves are superposed. This phenomenon is called ___________________ . It can be explained by the principle of superposition.

Principle of superposition of waves

1. The principle state that : When two waves interfered , the resulting of displacement of the medium at any location is the algebraic sum of the displacements of the individual waves.

2. At the moment when two crests or two troughs are completely __________________, the resulting shape of medium will be a crest or a trough with amplitude 2a.

3. This type of interference is called _________________________ interference .

4. On the other hand, if a crest of one wave propagates superposed on a trough of the second wave, , the resulting wave will cancel each other. There is no resulting disturbance in the medium .

5. This type of interference is called _____________________________ interference

6. Either constructive or destructive interference to occur, the waves must be coherent.

Diagram to show the transform of interference of waves7. The result for interference :

a. water waves

b. light waves

c. sound waves

8. Lines join places of constructive interference are called antinodal lines.

9. Lines join places of destructive interference are called nodal lines.

10. Interference of light can be produced by passing light through a double slit. An interference pattern consisting of alternate bright and dark fringes can be seen on a distance screen. These alternate bright bands is called as interference fringes.

11. Formula used in interference is where

a is the distance between two sources of waves

x is the separation between two adjacent nodes or antinodes

D is the perpendicular distance between waves source to the position where x is measured.

( is the wavelength of the used wave.

Diagram to show Youngs double slit experiment

Example 1

The diagram shows an arrangement in Youngs double slide experiment to show the

interference of light.

The wavelength of laser light used is 600 nm and the separation of the two slits is 0.48

mm. what is the separation of the fringes of the interference pattern?

Answer :

______________________________________________________________________Example 2

The diagram shows the fringes obtained from a double slit experiment using a

monochromatic light of wavelength 550 nm.

If the distance between the double slit and the screen is 1.5 m, what is the separation of

the double slit ?

Answer :

________________________________________________________________________Example 3

The diagram shows two circular water waves from two sources s1 and s2 overlapping as

they travel to the right. The circular lines indicate the crest lines of the water waves

What type of interference occurs at P, Q and R ?

P Q

R

A. constructiveconstructivedestructive

B. constructivedestructivedestructive

C. destructiveconstructiveconstructive

D. destructivedestructiveconstructiveExample 4

Diagram below show two identical speakers that are connected to an audio generator. The two speakers are a pair of coherent sources

A student walks along the line PQ which is 15 m away from the two loudspeakers. He hears a loud sound and a weak sound alternately

a) What is meant by coherent sources?

__________________________________________________________________________________________________________________________________

b) Calculate the wavelength of the sound wave

_________________________________________________________________c) The loud sound is caused by constructive interference of the sound waves. State the condition for constructive interference to occur?

__________________________________________________________________________________________________________________________________

d) The weak sound is caused by destructive interference of the sound waves. State the condition for a destructive interference to occur?

__________________________________________________________________________________________________________________________________

e) What is the effect of

i. Increasing the frequency of the sound wave

_________________________________________________________

ii. Decreasing the distance between the two loudspeakers

____________________________________________________Sound waves Sound propagate in a medium as longitudinal wavesLoudness and pitch

A high pitch sound corresponds to a high frequency and a low pitch sound corresponds to a low frequency of vibration

A loud sound corresponds to the amplitude of a sound. If we increase the amplitude of a sound, the sound will be louder.

Applications of sound waves

a) Ultrasonic spectacles__________________________________________________________________________________________________________________________________b) Sonar__________________________________________________________________________________________________________________________________c) Ultrasound scanner__________________________________________________________________________________________________________________________________Electromagnetic waves

Gamma ray, X-ray , ultraviolet, visible light, infrared, ,microwave and radio waves are parts of the electromagnetic spectrum

Electromagnetic waves travel at a speed of 3.0 x 108 ms-1Applications of electromagnetic waves

1. Radio wavesThere are various type of waves such as microwaves, VHF and UHF radio waves. Microwaves have the shortest wavelength, being a few centimeters. They are used in telecommunication as a transmitter. Radar systems are also use microwaves to find the direction and the distance of an object

2. Infrared

The remote control that use to switch on our electrical appliances such as the television, uses infrared. Infrared is also used in transmitting data between computers

3. X-rays

4. Gamma ray

5. Ultraviolet light

Question 1Figure below shows the electromagnetic spectrum

a) What names are given to the waves in sections labeled W and Q?

________________________________________________________________________b) From gamma ray to radio wave along the spectrum which property of the radiations has a decreasing value and which property has an increasing value

______________________________________________________________________c) State three common properties of all the electromagnetic waves

i. ______________________________________________________________ii. _______________________________________________________________iii. _______________________________________________________________MODULE 2

Form 52007waves

NAME.........................................................................

FORM FIVE.........................................................................

NAME OF TEACHER...........................................................................

Created by : Hjh Gayah Madu

SM Teknik Kluang 2007

a

a

A blade

a

Crests

troughs

Equilibrium position

Wavelength , (

a

Energy is transferred from the stone to the cork which does not involve the transfer of water.

The movement of the hand to the left and right is perpendicular to the direction of propagation of wave

Direction of propagation of wave

Direction of vibration

T

a

Direction of propagation of the wave

Direction of the vibration

T

rarefaction

compression

a

A

B

Direction of propagation of wave

wavefronts

EMBED Equation.3

Straight waves produced by a bar

A bar

( source)

Straight waves

Direction of propagation of wave.

EMBED Equation.3

.

A round dipper as the source of the wave.

or

Circular waves

displacement

a

distance

EMBED Equation.3

displacement

time

T

20_

-20_

0_

Displacement / cm

3 m

Distance ( m )

Time/s

20_

-20_

0_

Displacement / cm

1.2 s

dipper

Deep area

Shallow area

X Y

6 cm

dipper

i

r

normal

Incident wavefronts

Reflected wavefronts

i is called the angle of ______________________

r is called the angle of ____________________________

i 0 = r 0

Wavelength of the incident waves and the reflected waves are ________________

The incident waves and the reflected waves will have the same speed in water of equal depth

v, f and EMBED Equation.3 are remains constant in reflection

300

Incident ray

Refracted ray

normal

i

r

air

water

The angle between the incident ray and the normal is called the angle of incidence,____

The angle between the refracted ray and normal is called the angle of refraction , _____

When a wave passes through two medium with two different speed , the wave will ______ ( if i ( 00 )

This phenomenon is called as _____________________.

Refraction is due to the ________________ in the speed of wave when traveling from one medium to another medium

The wave will refracted ________________ the normal if it passes through a low speed medium to high speed medium and vice versa

Less dense high speed ; dense low speed ( for light waves )

Deep water high speed ; Shallow water low speed ( for water waves )

Dense high speed ; less dense low speed ( sound waves )

The frequency , f does not change in refraction

Shallow area

Deep area

Diagram to show diffraction when a wave pass through an opening

Diagram to show diffraction when a wave pass through an obstacles

A crest superposed a crest

A trough superposed a trough

=

=

2a

2a

+

+

a

a

a

a

A crest superposed a trough

=

Calm water.

+

Constructive interference - waves

Destructive interference calm water

Constructive interference bright fringe

Destructive interference dark fringe

Constructive interference loud sound

Destructive interference weak sound

screen

D= 1.2 m

Double slit

Laser light

24 mm

.

.

S1

S2

.

.

.

P

Q

R

Loud sound

Weak sound

Loud sound

Weak sound

Loud sound

Weak sound

Loud sound

Weak sound

Loud sound

6.8 m

Q

P

2.0 m

15.0 m

Loud speaker

Audio generator Coherent sources are two oscillating sources which have a constant phase difference.

Gamma rays

W

ultraviolet

Q

Infrared rays

microwaves

Radio waves

PAGE 1waves

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