Preliminary
Physics
The World Communicates
Lesson 1: Waves
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Name: _____________________
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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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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 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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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:
- 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:
Key competencies are embedded in the Physics Stage 6 Syllabus
Preliminary Course
HSC Course
The World Communicates
Electrical Energy in the
Home
Moving About
The Cosmic Engine
Space
Motors and Generators
From Ideas to
Implementation
Options:
- Geophysics - Medical physics - From quanta to quarks - The age of silicon - Astrophysics
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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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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 ALTEAST 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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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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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
Feedback
Reason Upwards
Foundational Proposition
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- 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:
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
Higher – order concept or principle
Analog
Target
Compared with
Feature
1 2 3
Feature
1 2 3
“ “ “ “ “ “
4
4
Cannot be compared with
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1. The Wave Model
CHECKPOINT:
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
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
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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 propogation.
There are types of waves studied in year 11. They are called:
- Mechanical
AND
- No mechanical
Explain what mechanical waves are.
- Provide two examples of mechanical waves.
Explain what non-mechanical waves are.
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Mechanical waves can be further classified into two categories: - Transverse
AND
- Longitudinal
There is only ONE TYPE Of non-mechanical wave and they are called ________________
- 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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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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- Wavefront
- Amplitude
Define the wavelength of a transverse wave.
- Wavelength can be denoted by the symbol 𝜆 also known as lamda
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Label the wave below for its crest, trough, amplitude, wavelength and equilibrium.
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2. Velocity of Waves
CHECKPOINT:
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:
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
𝒇 =𝟏
𝑻
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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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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:
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.
𝒗 = 𝒇𝝀
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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 × 108𝑚/𝑠. Red light has a wavelength of 7 × 10−7𝑚.
What is its frequency?
d) The frequency of violet light is 7.5 × 1014 Hz. What is its wavelength?
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e) 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.
Question 3 Compare mechanical waves to non-mechanical waves. (2 marks)
c
e f
a b
d g
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Question 4 Below are a number of series of waves. Underneath each diagram write the numbers of waves in the series.
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?
C
A B
D
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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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3. Different Energy Disturbances
CHECKPOINT:
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.
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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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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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. (3 marks)
Question 3
Illustrate two and three dimensional wave propagation. (2 marks)