Preliminary
Physics
The World Communicates
Lesson 1:
The Wave Model
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LESSON 1: The World Communicates
Preliminary Physics
Summary of Key Words
Account
Account for: state reasons for, report on. Give an account of: narrate a series of events or
transactions
Analyse
Identify components and the relationship between them; draw out and relate
implications
Apply
Use, utilise, employ in a particular situation
Assess
Make a judgement of value, quality, outcomes, results or size
Calculate
Ascertain/determine from given facts, figures or information
Clarify
Make clear or plain
Classify
Arrange or include in classes/categories
Compare
Show how things are similar or different
Construct
Make; build; put together items or arguments
Contrast
Show how things are different or opposite
Deduce
Draw conclusions
Define
State meaning and identify essential qualities
Demonstrate
Show by example
Describe
Provide characteristics and features
Discuss
Identify issues and provide points for and/or against
Distinguish
Recognise or note/indicate as being distinct or different from; to note differences
between
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LESSON 1: The World Communicates
Preliminary Physics
Evaluate
Make a judgement based on criteria; determine the value of
Examine
Inquire into
Explain
Relate cause and effect; make the relationships between things evident; provide why
and/or how
Extract
Choose relevant and/or appropriate details
Extrapolate
Infer from what is known
Identify
Recognise and name
Interpret
Draw meaning from
Investigate
Plan, inquire into and draw conclusions about
Justify
Support an argument or conclusion
Outline
Sketch in general terms; indicate the main features of
Predict
Suggest what may happen based on available information
Propose
Put forward (for example a point of view, idea, argument, suggestion) for consideration
or action
Recall
Present remembered ideas, facts or experiences
Recommend
Provide reasons in favour
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LESSON 1: The World Communicates
Preliminary Physics
Lesson Dotpoints
By the end of the lesson, you should understand the following concepts:
The Wave Model


Identify that mechanical waves require a medium for propagation while
electromagnetic waves do not
Define and apply the following terms to the wave model: medium,
displacement, amplitude, period, crest, trough, transverse waves, frequency,
wavelength, velocity
Velocity of Waves

Quantify the relationship between velocity, frequency and wavelength for a
wave:
𝑣 = 𝑓𝜆

Solve problems and analyse information by applying the mathematical model
of 𝑣 = 𝑓𝜆 to a range of situations
Different Energy Disturbances

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
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LESSON 1: The World Communicates
Preliminary Physics
The Physics Syllabus

During the preliminary course it is expected that students will develop skills
in:
- Planning and conducting investigations
- Communicating information and understanding
- Scientific thinking and problem-solving

The syllabus states that:
Key competencies are embedded in the Physics Stage 6 Syllabus
- This simply means that the syllabus is literally YOUR BEST FRIEND for both
preliminary and HSC physics
- All of your theory and practical exams at school are based on the Syllabus
dotpoints

Both the preliminary and HSC course have four topics in which you have to
master:
Preliminary
Course
HSC
Course
The World Communicates
Space
Electrical Energy in the
Home
Motors and Generators
Moving About
From Ideas to
Implementation
The Cosmic Engine
Options:
-
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Geophysics
Medical physics
From quanta to quarks
The age of silicon
Astrophysics
LESSON 1: The World Communicates
Preliminary Physics
Doing Well in HSC Physics

Physics is a pre-requisite for many university courses including:
-

Medicine
Engineering (some courses)
Science
Mathematics
These courses usually require ATARs above 95 meaning you need to know
how to maximise your marks
Study Techniques

There are a few study techniques that will indefinitely help you with
maximising your chemistry mark:
1. Study based on the syllabus and make sure you know it BACK TO FRONT
2. Always improve on your question answering skills. This means not only
practicing constantly but also being smart about it
-
Compare your answer with a sample answer and analyse until your
technique is perfect
-
Constantly practise using past paper exam questions as it helps you
consolidate your understanding
-
There are only so many types of questions they can ever ask you
meaning if you do enough past exams then you realise that the same
questions come up over and over again
3. Memorise KEY VERBS that are used to ask questions. The main ones
include:
-
Assess
Compare
Describe
Discuss
Explain
Justify
4. Memorise and understand key equations for physics as these can be used in
your explanations
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LESSON 1: The World Communicates
Preliminary Physics
Exam Techniques

Not only is studying technique very important, your exam technique is crucial
to doing well in physics
1. Remember to always make sure you understand what the question is asking
you
-
After lots of practise it might seem the question is easy but many times
the question is a little more trickier then what you originally perceived
-
Therefore, read the question AT LEAST TWICE
2. Read the verb they use to ask the question. For any question worth more
than 2 marks ALWAYS formulate a structure to answer the question.
3. When you encounter questions that are 5 marks or more ALWAYS spend a
few minutes and think about how you can answer the questions
4. Answer in dotpoints unless the question says otherwise
5. Draw accurate labelled diagrams and always use physics equations
wherever you can
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LESSON 1: The World Communicates
Preliminary Physics
First Principles Approach to Learning

To understand the physics course you want to learn from a first principles
approach

The first principles learning approach is a mode of inquiry that relentlessly
pursues the foundations of a problem

A first principles approach forms the basis of philosophy, mathematics and
physics

How can you think by first principles when solving problems?
Step 1

When looking at a problem always boil it down to the MOST BASIC truths
-
A basic truth is something that cannot be deduced from any other proposition
or assumption
-
For example, a basic or foundational statement could be “All men are mortal”
Step 2

Then reason upwards from these basic truths
-
For example, by saying “All men are mortal” we can also say that “Since
Einstein is a man, Einstein is mortal”
Step 3

Once you have reasoned upwards you need to have a feedback loop
-
This means you want to check or test your reasoning and then adjust your
reasoning
-
For example by saying that “Since Einstein is a man, Einstein is mortal”
-
To check your statement, you can confirm Einstein’s death on the 18th of April
1955
-
In this case a feedback loop is not necessary as you have confirmed your
reasoning
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LESSON 1: The World Communicates
Preliminary Physics
Feedback
Reason
Upwards
Foundational
Proposition
First Principles and Physics

In physics, a calculation is said to be from first principles if it starts directly at
the level of established laws of physics and does NOT make assumptions such
as:
- Empirical models
- Fitting parameters

For example, in year 12 physics (and extension 1 math) you will encounter
projectile motion questions
- Using a first principles approach is the easiest way to understand these
types of questions and almost guarantees you will get the answer correct
Analogies Approach to Learning

The analogies approach is the most common type of learning

It is an easier approach then the first principles approach as it does not
require much understanding

An analogies approach typically involves mapping between similar features of
concepts, principles and formulas
-
To simply state this, an analogy is a process of identifying similarities
between two concepts
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LESSON 1: The World Communicates
-

Preliminary Physics
One concept, which is familiar, is referred to as the analog, and other
concept, which is unfamiliar, is called the target
A useful representation of how an analogy works is shown below:
Higher – order concept or principle
Analog
Target
Compared with
Feature
Feature
1
2
3
“
“
“
“
“
“
Cannot be compared with
4
1
2
3
4

It is better to learn from a first principles approach rather than an analogies
approach

The first principles approach is particularly useful when you want to solve
problems. This skill is not practised by many but for those who are the ones
people label as ‘geniuses’. Think of:
-
Einstein
Steve Jobs
Elon Musk
Isaac Newton
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LESSON 1: The World Communicates
Preliminary Physics
1. The Wave Model
CHECKPOINT:

Identify that mechanical waves require a medium for propagation while
electromagnetic waves do not
Define and apply the following terms to the wave model: medium, displacement,
amplitude, period, crest, trough, transverse waves, frequency, wavelength,
velocity

What are Waves?

Waves are everywhere and we encounter them on a daily basis

Examples of waves include:
-
Sound waves
Visible light
Radio waves
Sine and cosine waves
Earthquakes

For most people, the concept of waves is from water moving in an ocean, lake
or pond

Waves in a pond are usually created by a disturbance such as a rock being
thrown into the water

The water then has a ___________ and a ____________ as it travels from one location
to another
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LESSON 1: The World Communicates

Preliminary Physics
The study of waves has been increasingly crucial to modern society as we use
waves to carry information
Energy Transformation

Waves are essentially a transfer of energy

The source of energy from a wave is essentially from a ________________

The wave transfers this energy from the vibration from one point to another

The transfer of energy is ALWAYS ___________ from the source of vibration

The term propagation is used to describe the movement of waves
-

Define propagation.
There are types of waves studied in year 11. They are called:
-
Mechanical
AND

Explain what mechanical waves are.
-

No mechanical
Provide two examples of mechanical waves.
Explain what non-mechanical waves are.
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LESSON 1: The World Communicates

Preliminary Physics
Mechanical waves can be further classified into two categories:
-
Transverse
AND

There is only ONE TYPE Of non-mechanical wave and they are called
____________________________
-

Longitudinal
Why are these types of waves non-mechanical?
Electromagnetic radiation can propagate through the vacuum of space
-
Can mechanical waves propagate through space? Explain.
-
Can non-mechanical waves propagate through medium? Explain.
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LESSON 1: The World Communicates
Preliminary Physics
Transverse Waves

Transverse waves are waves in which the particles vibrate at right angles to
the direction of wave’s velocity or propagation

An example of this type of wave is the pulse travelling along a slinky as it is
being shaken


Using the slinky as an example we can describe what a transverse wave looks
like
All transverse waves ripple in the shape of a ________________

We can name and measure a number of waves features

For each of the following definitions describe what part of the transverse wave
they belongs to:
-
Crests
-
Troughs
-
Equilibrium or mean
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LESSON 1: The World Communicates

-
Wavefront
-
Amplitude
Define the wavelength of a transverse wave.

Preliminary Physics
Wavelength can be denoted by the symbol 𝜆 also known as ______________
Label the wave below for its crest, trough, amplitude, wavelength and
equilibrium.
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LESSON 1: The World Communicates
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Preliminary Physics
16
LESSON 1: The World Communicates
Preliminary Physics
2. Velocity of Waves
CHECKPOINT:

Quantify the relationship between velocity, frequency and wavelength for a wave:
𝑣 = 𝑓𝜆

Solve problems and analyse information by applying the mathematical model of
𝑣 = 𝑓𝜆 to a range of situations
Frequency of a Wave

Since every mechanical wave has a vibrating source, the rate at which the
source vibrates directly affects the nature of the wave formed

The frequency of a wave is the source is number of _________________ or ___________
that are completed per second at a fixed point

The following formula can be used to define frequency:

For example, if it takes a wave ½ second to pass through a point, the frequency
is found to be ________________

If it takes 1/100 of an hour, the frequency is 100 per hour.

Label whether the following are high or low frequency:
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LESSON 1: The World Communicates
Preliminary Physics
Period of a Wave

The period of a wave is linked to its ________________

The period is the time interval for one vibration or cycle
-
The period is measured in ______________

Consider a particle at the mean or equilibrium position initially.

The particle starts rising till it reaches a peak called crest, then starts falling till
it reaches the lowest point crossing the mean position.

The lowest point is called __________________

Again it starts rising and reaches the mean position. In other words the particle
has completed one cycle of wave motion.

This cycle repeats in a uniform pattern along with time.

Therefore, the period can be defined as:

Rearrange the formula for frequency to find the formula for period.
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LESSON 1: The World Communicates
Preliminary Physics
Velocity of a Wave

The velocity of a wave deals with how fast the wave transfers energy AWAY
from a source

The velocity can be calculated if the wavelength and frequency are known

The formula for the velocity of a wave is shown below:
𝒗 = 𝒇𝝀
Example

The wave in the sea has a wavelength of 15m. The frequency those waves
passing through a fixed point is measured to be 2Hz. Calculate the velocity of
wave.
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LESSON 1: The World Communicates
Preliminary Physics
Applications 2.1
Question 1
a)
A tuning fork has a frequency of 280 hertz and the wavelength of the sound
produced is 1.5m. Calculate the velocity of the wave.
b)
A wave is moving toward shore with a velocity of 5.0m/s. If its frequency is
2.5 hertz, what is the wavelength?
c)
The speed of light is 3.0 × 108 𝑚/𝑠. Red light has a wavelength of 7 × 10−7 𝑚.
What is its frequency?
d)
The frequency of violet light is 7.5 × 1014 Hz. What is its wavelength?
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LESSON 1: The World Communicates
e)
Preliminary Physics
A jump rope is shaken producing a wave with a wavelength of 0.5m with the
crest of the wave passing a certain point 4 times per second. What is the
velocity of the wave?
Question 2
The illustration below shows a series of transverse waves. Label each part in the
space provided.
a
b
c
f
e
d
g
Question 3
Compare mechanical waves to non-mechanical waves. (2 marks)
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LESSON 1: The World Communicates
Preliminary Physics
Question 4
Below are a number of series of waves. Underneath each diagram write the
numbers of waves in the series.
B
A
D
C
a) Which of the above has the biggest amplitude?
b) Which of the above has the shortest wavelength?
c) Which of the above has the longest wavelength?
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LESSON 1: The World Communicates
Preliminary Physics
Question 5
a)
Whales in the ocean omit sound waves to one another that can travel
enormously long distances. If two whales are 1500.0 km apart and omit sounds
have a frequency of 19 kHz and a wavelength of 0.0805 metres. How much
time will it take the sounds to travel from one whale to another whale? (3
marks)
b) A piano emits frequencies that range from a low of about 28 Hz to a high of
about 4200 Hz. Find the range of wavelengths attained by this instrument.
Assume speed of sound to be 340 m/s.
Question 6
a)
What is the wavelength of a radio wave that has a frequency of 96.5 Mhz?
(2 marks)
b) What is the period of the radio wave?
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LESSON 1: The World Communicates
Preliminary Physics
3. Different Energy Disturbances
CHECKPOINT:

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
Waves in Different Dimensions

Depending on the type of wave and the medium in which they are travelling,
waves may travel in one, two or three dimensions
One Dimension

One dimensional waves travel only in one direction

They are occur as transverse or longitudinal waves

Provide an example of a one dimensional wave.
Two Dimension

Two dimensional waves travel in two directions

An example of two dimensional waves is when a pebble is thrown into a still
pond

Label the point source of the wave and the wavefronts.
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LESSON 1: The World Communicates
Preliminary Physics
Three Dimension

Three dimensional waves travel in all directions

One example of 3D waves is sound travelling from an ambulance
- What type of waves are sound waves? Explain your answer.

Identify three dimensional waves from space.

Draw a diagram to show three dimensional wave motion.

Identify the type of wave energy being released by stars.
- What type of waves are EMR waves? Explain your answer.
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LESSON 1: The World Communicates
Preliminary Physics
Applications 3.1
Question 1
Provide an example for each of the following:
a)
One dimensional wave
b)
Two dimensional wave
c)
Three dimensional wave
Question 2
Compare the propagation of waves between one, two and three dimensions.
(2 marks)
Question 3
Illustrate two and three dimensional wave propagation. (2 marks)
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