Year 11 Physics Topic 3: The World Communicates Start date: ________________

8.2 The World Communicates (Dot Point 1)

Contextual Outline

Humans are social animals and have successfully communicated through the spoken word, and then, as the use of written codes developed, through increasingly sophisticated graphic symbols. The use of a hard copy medium to transfer information in coded form meant that communication was able to cross greater distances with improved accuracy of information transfer. A messenger was required to carry the information in hard copy form and this carrier could have been a vehicle or person. There was, however, still a time limit and several days were needed to get hard copy information from one side of the world to the other.

The discovery of electricity and then the electromagnetic spectrum has led to the rapid increase in the number of communication devices throughout the twentieth century. The carrier of the information is no longer a vehicle or person — rather, an increasing range of energy waves is used to transfer the message. The delay in relaying signals around the world is determined only by the speed of the wave, and the speed and efficiency of the coding and decoding devices at the departure and arrival points of the message. The time between sending and receiving messages through telecommunications networks is measured in fractions of a second allowing almost instantaneous delivery of messages, in spoken and coded forms, around the world.

This module increases students’ understanding of the nature, practice, application and uses of physics and current issues, research and developments in physics.

Dot Point 1:

1. The wave model can be used to explain how current technologies transfer information

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1.1 describe the energy transformations required in one of the following:– mobile telephone– fax/modem – radio and television An energy transformation is a change in the type of energy, for example a change from sound energy to electromagnetic waves. Question 1a): Describe energy transformation in the mobile telephone: ______________________ _____________________________________________________________________________

Mobile telephone:

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Question 1b) Define the terms energy and wave.

Question 2b) Explain how energy is transferred in a water wave without moving the individual water molecules.

1.1.2 describe waves as a transfer of energy disturbance that may occur in one, two or three dimensions, depending on the nature of the wave and the medium

Question 2: - Waves are carriers of energy. Waves may be 1D, 2D, or 3D. Examples of each include; laser light, which is a one dimensional wave; water waves, which are two dimensional waves; and sound waves, which spread out in all directions from a point, so are therefore three dimensional waves.

Complete the table to summarise one-dimensional (1-D), two-dimensional (2-D) and three-dimensional (3-D) waves.

Types of waves Example Medium Description

1-D Travels in one direction along aline

2-D Ripples on a pond

3-D Air

1.1.3 identify that mechanical waves require a medium for propagation while electromagnetic waves do not

Mechanical waves, such as sound waves, water waves and earthquake waves need a medium (a substance) to travel through, they cannot move from one point to another if there is nothing (a vacuum) between the two points. On the other hand electromagnetic waves do not need a medium to travel through. An example of this is in space, which is a vacuum, if you call out in space your sound waves do not penetrate out of your space suit. However electromagnetic waves do, therefore you can see the light from the sun. Even simpler, in space you can see a planet explode, but you cannot hear it.

Question 3 (a) Identify the property that is common to all mechanical waves.Question 3 b) Identify three examples of EM waves.uestion 3 (c) Compare EM and mechanical waves. (Use a table – similarities, difference and examples)

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1.1.4 define and apply the following terms to the wave model: medium, displacement, amplitude, period, compression, rarefaction, crest, trough, transverse waves, longitudinal waves, frequency, wavelength, velocity

Medium: The substance through which the wave travels through.Displacement: Is the distance from the rest position to the wave particle at that instant. Amplitude: The distance from the rest position to the highest crest or the lowest trough. Period: The time it takes for one wavelength to pass a point. Period = 1/ frequency Compression: In compression waves, the space where the particles are closest together. Rarefaction: In compression waves, the space where the particles are furthest apart. Crest: The parts of the wave that are above the rest position. Trough: The parts of the wave which are below the rest position. Transverse waves: Are forms of mechanical waves, they involve the particles vibrating perpendicular to the direction of the wave. Longitudinal waves: Are also forms of mechanical waves, and they involve the particles vibrating along the direction of the wave. Frequency: Frequency is the number of waves that pass a point in one second. Frequency = 1/periodWavelength: The distance of one full wave. Velocity: The speed that the wave is propagating. (see 1.1.6 for the relationship between velocity, frequency and wavelength)

Question 4 (a) Compare the direction of oscillation and the direction of energy transfer in a longitudinal wave and a transverse

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Question 4 (b) Compare the direction of oscillation and the direction of energy transfer in a longitudinal wave and a transversewave. Use diagrams in your answer.Question 4 (c) Draw and label a diagram of a sinusoidal wave to clearly illustrate the crest, trough, amplitude and wavelength. Use diagrams in your answer.Question 4 (d) Draw and label a a sinusoidal wave to clearly illustrate the crest, trough, amplitude and wavelength. http://www.bbc.co.uk/bitesize/standard/physics/telecommunications/communication_using_waves/revision/5/http://www.softschools.com/quizzes/science/waves/quiz343.html wave to clearly illustrate the crest, trough, amplitude and wavelength.

1.1.5describe the relationship between particle motion and the direction of energy propagation in transverse and longitudinal waves In longitudinal waves the particle motion is in the parallel to the direction of the energy propagation. On the other hand in transverse waves the particle motion is perpendicular to the direction of the energy propagation.

1.1.6 quantify the relationship between velocity, frequency and wavelength for a wave: v f The velocity of a wave is equal to the frequency multiplied by the wavelength. v f 𝑓 is in Hz, 𝜆 is in m and 𝑣 is in ms−1 .

V= velocity in m/s, f = frequency in Hertz and symbol is Hz and 𝝺 = wavelength in metres

Question 5: Imagine that you are on a boat in the middle of the ocean and you are bobbing up, down andup again once every 2 s due to the water waves. You notice that the crests of the waves areabout 10 m apart.

(a) Calculate the frequency of the waves.(b) Calculate the speed of the waves.

perform a first-hand investigation to observe and gather information about the transmission of waves in:– slinky springs– water surfaces– ropesor use appropriate computer simulations

(refer to practical booklet)

Question 6:

Increasing or reducing the tension in a rope can change the speed of a wave travelling along it. Predict how thewavelength changes for a wave on the rope if:a the frequency and speed are both halvedb the speed is doubled and the period remains the samec the speed remains the same but the period is doubled.

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present diagrammatic information about transverse and longitudinal waves, direction of particle movement and the direction of propagation

1.2.2 perform a first-hand investigation to gather information about the frequency and amplitude of waves using an oscilloscope or electronic data-logging equipment

(refer to practical booklet)

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Name: ________________________________________ Date: __________

Year `22 Physics Topic 2 Waves:

1.2.3 present and analyse information from displacement-time graphs for transverse wave motion

https://www.classzone.com/books/ml_science_share/vis_sim/wslm05_pg18_graph/wslm05_pg18_graph.html

http://www.animations.physics.unsw.edu.au//jw/oscillations.htm#physics

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Answer:

1.2.4 plan, choose equipment for and perform a first-hand investigation to gather information to identify the relationship between the frequency and wavelength of a sound wave travelling at a constant velocity

1.2.4 solve problems and analyse information by applying the mathematical model of

to a range of situations

(see questions next page)

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Summary:• Wave is any vibration (or oscillation) that can travel (propagate) from one place to another.• Waves can be used to carry energy and information.• A medium is an object or material through which the wave propagates, such as air for sound waves.• All waves that require a material object as the medium are called mechanical waves.• Transverse waves occur when the particles of the medium move (displace) at right angles to the direction of wave propagation, such as waves on a rope.• Longitudinal (or compression) waves occur when the particles of the medium move (displace) along thesame direction as the wave propagation; for example, compressing part of a slinky spring makes a longitudinal wave.• The transfer of energy by a wave can take place in one, two or three dimensions, such as a rope (1-D), watersurface waves (2-D) or soundwaves (3-D).• Electromagnetic waves can propagate in three dimensions and do not require a medium. In a vacuum,these waves travel at the speed of light and are used in communication equipment, such as mobile phones.• Electromagnetic waves include radio waves, microwaves, infra-red rays, visible light, ultraviolet rays, X-rays andgamma rays.• Electromagnetic waves are transverse waves, where the electric and magnetic fields are at right angles to eachother and to the direction of wave propagation.• Mobile phone communication involves the transfer of energy between mechanical, electrical and electromagnetic energies.• All waves can be described by combinations of sine waves.• The maximum distance a particle oscillates from its equilibrium position (at either a peak or trough) isthe amplitude.• The distance between a peak (or trough) and its nearest neighbour is called wavelength λ.)• The number of peaks (or troughs) that pass a point per second is called the frequency (f ). The unit of frequencyis cycles per second or hertz (Hz).• The time in seconds between two adjacent peaks (or troughs) is called period (T ).• Frequency is the reciprocal of period: f • Wave speed (v) is given by v f .

Quiz 1:

1. What is a wiggle in time called? ___________ What is a wiggle in space and time called? _________2. What is the period of a pendulum? ___________________________________3. What is the period of a pendulum that takes one second to make a complete back-and-forth vibration? ________ 4. Suppose that a pendulum has a period of 1.5 seconds. How long does it take to make a complete back and forth

vibration? Is this 1.5-second period longer or shorter in length than a 1-second period pendulum? __________5. How is a sine curve related to a wave? _____________________________ 6. Distinguish among the different parts of a wave: amplitude, crest, trough, and wavelength. Amplitude – ________________________ ; crest – ______________________________ ; trough ________________________; wavelength – ________________________________ 7. Distinguish between the period and the frequency of a vibration of a wave. How do they relate to one another?

Period – ________________________ ; frequency – ___________________________

8. Does the medium in which a wave travels move along with the wave itself? ____________________ Defend your answer. ________________________________________________ 9. How does the speed of a wave relate to its wavelength and frequency? _____________________________

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10. As the frequency of sound is increased, does the wavelength increase or decrease? ________________ Give an example. ___________________________________

11. Distinguish between a transverse wave and a longitudinal wave. Transverse – ______________________________

longitudinal – ____________________________________________

12. The diagram shows a transverse wave.

a) Which of A, B, C or D is:

i) the wavelength

ii) the amplitude

Classwork/ Homework:1. Identify the main energy types used in the communication methodslisted below.a satelliteb mobile phonec televisiond radioe fax

2. Complete the following table to summarise the transmitter, transport medium/method and receiver for each device.

Device TRANSMITTER TRANSPORTMEDIUM/METHOD

RECEIVER

RadioMobile phoneLandline phone

3. Classify each of the following as mechanical or electromagnetic (EM) waves and whether they are one-, two- or three-dimensional.

Device Mechanical or EM wave Dimension (1D, 2D or 3D)RadioMobile phoneLandline phone

4. Wave speed = frequency x wavelength1. Calculate the speed of a wave that has a frequency of 50 Hz and a wavelength of 4 m.2. Calculate the speed of a wave that has a frequency of 200 Hz and a wavelength of 50 m3. Calculate the speed of a wave that has a frequency of 6 Hz and a wavelength of 2000 m4. Calculate the speed of a wave that has a frequency of 0.5 Hz and a wavelength of 0.2 m

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6. Calculate the speed of a wave that has a frequency of 5 kHz and a wavelength of 4 m7. Calculate the speed of a wave that has a frequency of 5 Hz and a wavelength of 50 cm8. Calculate the speed of a wave that has a frequency of 2 M Hz and a wavelength of 4 m9. Calculate the speed of a wave that has a frequency of 4 M Hz and a wavelength of 8 cm10. Calculate the speed of a wave that has a frequency of 3 G Hz and a wavelength of 4 mm

Answer to Quiz 1:

1. What is a wiggle in time called? What is a wiggle in space and time called? A vibration; A wave2. What is the period of a pendulum? Time for one complete cycle to occur3. What is the period of a pendulum that takes one second to make a complete back-and-forth vibration? 1 s 4. Suppose that a pendulum has a period of 1.5 seconds. How long does it take to make a complete back and forth

vibration? Is this 1.5-second period longer or shorter in length than a 1-second period pendulum? 1.5 s; longer5. How is a sine curve related to a wave? A sine curve is a pictorial representation of a wave 6. Distinguish among the different parts of a wave: amplitude, crest, trough, and wavelength. Amplitude –

maximum displacement; crest – point of greatest positive displacement; trough – point of greatest negative displacement; wavelength – distance from one crest to the next

7. Distinguish between the period and the frequency of a vibration of a wave. How do they relate to one another? Period – time to complete one cycle; frequency – how many cycles occur in a given time

8. Does the medium in which a wave travels move along with the wave itself? Defend your answer. No. The disturbance, not the material itself, moves

9. How does the speed of a wave relate to its wavelength and frequency? Speed = wavelength x frequency 10. As the frequency of sound is increased, does the wavelength increase or decrease? Give an example.

Decreases; smaller musical instruments produce higher frequency sounds 11. Distinguish between a transverse wave and a longitudinal wave. Transverse – medium moves perpendicular to

wave direction; longitudinal – medium moves back and forth parallel to wave direction

WavesAnswer Question 1:Relating this to the mobile telephone, it undergoes basic energy transformations of, sound wave (your voice), to electrical energy (in the wires inside the phone), to electromagnetic waves (from the phone to the tower), to electrical energy (at the tower), then to electromagnetic waves (to reach the receiving phone), then electrical energy (inside the receiving phone), then to sound waves (at the speaker of the receiving phone).

Question 2:

Types of waves Example Medium Description

1-D Travels in one direction along aline

2-D Ripples on a pond

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3-D Air

Question 3:

Types of waves Mechanical waves 2nd example

1-D

2-D

3-D

Question 4:Types of waves 1st example 2nd example

similarities

differences

examples

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Question 5:

Quetsion 6 Example Problem: Question: An FM radio station transmits a carrier wave of frequency 103.2 MHz. Calculate the wavelength of the signal.

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