preliminary physics - leaders in the hsc · pdf filepreliminary physics the world communicates...

Preliminary

Physics

The World Communicates

Lesson 1: The Wave Model

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Name: _____________________

LESSON 1: The World Communicates Preliminary Physics

Copyright © HSC Synergy Education 2016

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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 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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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 propagation.

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 ______________

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



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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. (2 marks)

Question 3

Illustrate two and three dimensional wave propagation. (2 marks)

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