VCE Physics Units 3&4
Presented by:ALEVINE MAGILA
Exam Revision
Lecture
• Introduction
• How do things move without contact?
• How are fields used to move
electrical energy?
• How fast can things go?
• How can waves explain the behavior
of light?
• How are light and matter similar?
• Final tips and tricks
• Introduction
• How do things move without contact?
• How are fields used to move
electrical energy?
• How fast can things go?
• How can waves explain the behavior
of light?
• How are light and matter similar?
• Final tips and tricks
So then what can I provide in this lecture?
• Detailed look at VCAA Exam structures and styles
• Help you to identify any weaknesses you have
• Explain hard ‘separator’ questions from VCAA
• Strategies to tackle hard questions
• General advice from a past student
If what you’re looking for is content and revision summaries, have a look at
the course notes or topic tests.
Today’s Lecture
4
• Introduction
• How do things move without contact?
• How are fields used to move
electrical energy?
• How fast can things go?
• How can waves explain the behavior
of light?
• How are light and matter similar?
• Final tips and tricks
Magnetic Field Vectors
6
2011 Physics Exam 2
Magnetic Field Vectors
7
2011 Physics Exam 2
Magnetic Field Vectors
8
2013 Physics Exam
Satellite Motion
9
2013 Physics Exam
Astronauts in orbit only have one force acting on them: the weight force.
Therefore,
Σ𝐹 = 𝐹𝑔
Σ𝐹 =𝐺𝑀𝑚
𝑅2= 𝐹𝑔
SATELLITE MOTION
10
In year 12, we model satellite motion as uniform circular motion. We can account
for this in our equations:
Σ𝐹 =𝑚𝑣2
𝑅=𝐺𝑀𝑚
𝑅2= 𝐹𝑔
Σ𝐹 =𝑚𝑣2
𝑅=4𝜋2𝑅
𝑇2=𝐺𝑀𝑚
𝑅2= 𝐹𝑔
𝑎 =𝑣2
𝑅=4𝜋2𝑅
𝑇2=𝐺𝑀
𝑅2= 𝑔
Satellite Motion
11
2013 Physics Exam
DC Motors
12
2014 Physics Exam
DC MOTORS
13
DC Motors
14
2014 Physics Exam
DC Motors
15
2014 Physics Exam
Explanation Questions
16
The best advice I’ve heard when it
comes to explanation-style
questions?
Be specific, and answer the question.
DC Motors
17
2014 Physics Exam
• Magnetic forces act on the coil create a torque.
• This torque causes the magnetic field to rotate
DC Motors
18
2016 Physics Exam
• The magnetic forces acting on the coil are at a
maximum when the coil is at a flat, horizontal
position
• Therefore, a horizontal position if the best position
for the motor to start from rest
Charged Particles Moving Through a
Magnetic Field
19
A moving charge in a magnetic field will experience a magnetic force. This
force can be calculated from the equation
𝐹 = 𝑞𝑣𝐵From Newton’s second law, we know that whenever there is a net force, there
is an acceleration. Since there is a net magnetic force on a moving charge
through the magnetic field, it must be accelerating.
In reality, a moving charge does not change speed through a magnetic field –
it changes direction. Therefore, charged particles experience a centripetal
acceleration when they move through a magnetic field.
This yields the equation
𝑚𝑣2
𝑅= 𝑞𝑣𝐵
The direction of the magnetic force on a charged particle can be calculated
using the right-hand slap rule, except this time, the thumb points in the
direction of the charge’s velocity instead of in the direction of the current.
If the charge is negative, the thumb points in the opposite direction to the
charge’s velocity.
Particle Accelerators
20
Weight Force/ Normal Force In
Satellites
21
2016 Physics Exam
• It is possible to experience weightlessness without being truly
weightless
• This occurs when the normal force acting on someone is 0 i.e
they are in freefall
• This gives them the sensation of being weightless, known as
apparent weightlessness
• Thus Emily is incorrect – it IS possible to FEEL weightless without
needing to be in deep space
Graph of Gravitational Force vs
Distance
22
2002 Physics Exam
• There are approximately
13 squares
• Each square has a value
of 1000 x 3 x 106 = 3 x
109 J
• Therefore, the total energy
required equals 13 x 3 x
109 J
• Introduction
• How do things move without contact?
• How are fields used to move
electrical energy?
• How fast can things go?
• How can waves explain the behavior
of light?
• How are light and matter similar?
• Final tips and tricks
Faraday’s Law
24
2015 Physics Exam
Induced EMF
25
2011 Physics Exam 2
Transformers
26
2014 Physics Exam
Making calculations about an electrical generator (such as calculating the
average power it produces) can be tricky because induced EMF is always
varying.
To compensate for this, physicists sometimes like to use a quantity called
the root mean square or RMS voltage.
This is the DC voltage it would take to produce the same average power as
an oscillating AC voltage.
To find the RMS voltage, we use the formula
𝑉𝑅𝑀𝑆 =𝑉𝑝
2
𝑉𝑝𝑒𝑎𝑘 is the ‘peak’ voltage or the maximum voltage induced (this can be
read from a graph or an oscilloscope).
PEAK VOLTAGE AND RMS VOLTAGE
27
Transmission of Electricity
28
Transmission of Electricity
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• Transformers significantly increases voltages to very high levels
• For a constant power, the voltage and the current are inversely
proportional (P = IV)
• An increase in voltage causes a decrease in current
• Decreasing the current decreases the power loss (𝑃𝑙𝑜𝑠𝑠 = 𝐼2𝑅), thereby reducing transmission losses
• Introduction
• How do things move without contact?
• How are fields used to move
electrical energy?
• How fast can things go?
• How can waves explain the behavior
of light?
• How are light and matter similar?
• Final tips and tricks
Pulley Questions
31
Pulley Questions
32
Banked Tracks
33
When working through banked track problems, here are some
useful tips when through these types of questions:
• Draw a diagram (if one isn’t already supplied to you)
• Draw a force triangle. Again, the only forces acting on the
car that is moving at the design speed should be the weight
force and the normal force
• Note that for many questions, you won’t actually need the
mass of the car to find the answer
Tackling Banked Track Problems
34
Vertical Circular Motion
35
Length Contraction
39
Muons
40
Muons
41
• Why did the experiments
observe more muons
than expected?
• Because the half-life of
the muons, relative to the
experimenters, increased.
• This led to a higher
number of muons
reaching the detector
without decaying
• Introduction
• How do things move without contact?
• How are fields used to move
electrical energy?
• How fast can things go?
• How can waves explain the behavior
of light?
• How are light and matter similar?
• Final tips and tricks
The Doppler Effect
43
Emily is waiting to cross the road when an ambulance swerves around the corner with its sirens blaring. When the ambulance rushes towards Emily, the pitch of the siren seems to increase. As the ambulance passes Emily and drives into the distance, the pitch of the siren seems to decrease. Explain this effect.
• The change in pitch of the siren is due to the Doppler Effect
• As the ambulance approaches Emily, each consecutive sound
wave produced by the siren is slightly closer to her than the one
before, creating an apparent increase in frequency.
• Conversely, when the ambulance drives away from Emily, each
consecutive sound wave is slightly further away from Emily that
the one before, causing the apparent frequency to decrease.
• This causes the change in pitch of the siren that Emily hears.
Resonance
44
A wine goblet is able to shatter when certain frequencies of sound impinge upon it. Explain how this is possible.
• When sound with a frequency equal to the natural frequency of the
wine glass impinges on the goblet, resonance occurs.
• During resonance, all the energy from the source of the sound is
transferred to the wine glass. If enough energy is supplied by the
source, the glass’ vibrations become too large, causing it to shatter.
Standing Waves
45
A pipe organ can be modelled as a tube open at one end and closed at the other. If the length of one particular pipe organ is 1.5 m, calculate the frequency of the fourth harmonic the organ can produce. Assume the speed of sound in the organ is equal to 343 m s-1.
Polarization
46
Polarizing sunglasses are popular amongst athletes in winter sports as they help reduce glare and improve vision. Explain how polarizing sunglasses do this.
• Polarizing sunglasses restrict the light waves entering the lens so
that only light waves with a certain orientation are able to pass
through.
• Light waves that do not have the correct orientation are blocked,
which is what helps to reduce glare for the sunglass users.
Refraction
47
During a pool party in the evening, Betty turns the underwater lights on at the bottom of her pool to help her guests see where they are swimming. At some angles, the light is refracted in such a way at the water-air interface that it becomes parallel to the surface of the pool. What is this angle? Assume nwater = 1.33
Dispersion
48
When white light is passed through a glass prism, it ‘splits’ into its component colors. Identify this physics phenomenon and explain why it occurs.
• Every colour of light undergoes refraction to a slightly different
extent due to the differences in wavelength.
• White light is composed of all the colours of the visible spectrum.
• When it is passed through a glass prism, all the component
colours of white light refract to a slightly different extent.
• This causes the white light to ‘split’ and is known as dispersion.
Young’s Double-Slit Experiment
49
Young’s Double-Slit Experiment
502015 Physics Exam
• The distance between the central band and each of the slits is the
same. Therefore, the path difference to the central band is 0.
• The path difference can only be 0 if it is of the form n𝜆 – not (n −0.5)𝜆.
• Since n𝜆 corresponds to constructive interference, the central band on
the screen must be a bright band
Young’s Double-Slit Experiment
51
2013 Physics Exam
• The appearance of the diffraction pattern of the screen in Young’s Double-Slit
experiment proves that light is able to undergo constructive and destructive
interference
• Interference is strictly a wave phenomena – it cannot be exhibited by particles.
• Therefore, Young’s Double-Slit experiment provides evidence for the wave
model of light – not the particle model. The statement is incorrect.
• Introduction
• How do things move without contact?
• How are fields used to move
electrical energy?
• How fast can things go?
• How can waves explain the behavior
of light?
• How are light and matter similar?
• Final tips and tricks
The Photoelectric Effect
54
• The wave model of light predicts that increasing the intensity of the light
increases the amount of energy supplied to the electrons, allowing them to
escape from the metal plate. However, this did not happen.
• The particle model for light predicts that increasing the intensity of light
increases the number of photoelectrons released, not their energy. So there is
still not enough energy to release electrons from the metal plate.
Observations vs Predictions
THE PHOTOELECTRIC EFFECT
55
Observations
1. There is a frequency called the
threshold frequency, f0, that
below which, there will be no
photoelectrons emitted.
2. Increasing the intensity of light
increases the number of
photoelectrons released.
3. Photoelectrons are released
instantaneously.
Predictions
1. All frequencies of light should
eventually be able to emit
photoelectrons
2. Increasing the intensity of light
increases the kinetic energy of
released photoelectrons
3. Photoelectrons are released
with some time delay
Electron Diffraction Pattern
Question
56
2012 Physics Exam
Electron Diffraction Pattern
Question
57
2012 Physics Exam
Atomic Emission/ Absorption
58
De Broglie’s Mode of the Atom
59
2014 Physics Exam
• Electrons are only stable is they form standing waves around the nucleus of
an atom.
• There are only some wavelengths of an electron matter wave that can form
standing wave
• As a result, there are only certain energy levels that an atom can occupy; -
the energy of atoms is quantized.
HEISENBERG’S UNCERTAINTY
PRINCIPLE
60
• Increasing the slit width will increase the range of possible positions the photon could be in as
it passes through the slit; it increases Δ𝑥.
• By Heisenberg’s Uncertainty Principle, an increase in Δ𝑥 will result in a decrease in Δ𝑝 (Δ𝑥
Δ𝑝 ≥ℎ
4𝜋)
• An increase in the uncertainty in momentum means that photons have a higher chance of
passing through the slit at wider angles. This effectively increases the width of the diffraction
pattern on the screen.
• Introduction
• How do things move without contact?
• How are fields used to move
electrical energy?
• How fast can things go?
• How can waves explain the behavior
of light?
• How are light and matter similar?
• Final tips and tricks
Storing Values on your Calculator
62
To store values on your calculator
1. Enter the value you want to store and
press ‘equals’
2. Click ‘shift’ and then ‘STO’ (it’s above
the RCL key)
3. Click on the letter you want to store the
value in.
4. Press equals again
• Do as many practice exams as you possibly can for physics
• Do practice exams in exam conditions i.e no phones, near
silence, clock on the wall etc.
• Identify and focus on improving your weakest areas
• Learn from your mistakes; understand the questions you
get wrong and learn from them
• Practice ‘explain’ style questions
• Use your scientific calculator when doing physics
• Eat healthy, get exercise and sleep consistently
Before the Exam
63
• You don’t have to do the exam in chronological order. In some cases, it
may be better to start with your strongest area of study. This leaves you
more time during the exam to focus on your weaker areas.
• Aim for a minute a mark. You want left over time at the end to check
over all your answers
• Never stop checking your work. If you have time at the end, then do not
stop checking your work until the time for the exam has ended
• If there’s a question that you’ve spent more that two minutes looking at
but still don’t know how to do – skip it. Your time is better spent
finishing the exam and then coming back to it later
• NEVER, ever leave anything blank. If you’re nearly finished and there
are still a few questions that your not sure how to do, take a guess!
Never leave any questions blank
During the Exam
64
Can I do well in VCE Physics if I…
• Spend every waking minute doing physics exams and every sleeping
minute dreaming of physics textbooks
• Do a unit 3 and unit 4 exam for revision every week
• Try a practice exam every week or so but nothing else
• Only read the textbook and try textbook questions
• Just attend a VCE Physics revision lecture
Difficulty Of VCE Physics
65
How To Succeed In VCE Physics
66
Good Luck!
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If there are any questions you have from today, or if you want me
to go into a topic in more detail, don’t hesitate to ask me!!
Alevine Magila