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PHYSICS, M8 2023 HSC 33

Consider the following statement.

The interaction of subatomic particles with fields, as well as with other types of particles and matter, has increased our understanding of processes that occur in the physical world and of the properties of the subatomic particles themselves.

Justify this statement with reference to observations that have been made and experiments that scientists have carried out.   (9 marks)

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Thomson’s Experiment:

  • Thomson’s experiment tested the interaction of cathode rays (which he discovered were negatively charged subatomic particles and named them electrons) with electric and magnetic fields to determine the charge to mass ratio (\(\dfrac{q}{m}\)) of the electrons.
  • Using both the electric and magnetic fields, Thomson balanced the forces to ensure the cathode rays travelled through undeflected. Thus:
  •    \(F_E = F_B \ \ \Rightarrow \ \ qE=qvB \ \ \Rightarrow \ \ v=\dfrac{E}{B}\)
  • Using the magnetic field and known velocity, the cathode rays travelled in a circular path due to their negative charges interacting with the magnetic field. Thus:
  •    \(F_c=F_B\ \ \Rightarrow \ \ \dfrac{mv^2}{r}=qvB \ \ \Rightarrow \ \ \dfrac{q}{m}=\dfrac{v}{Br}\)
  • The charge to mass ratio was determined to be 0.77 \(\times\) 10\(^{11}\) Ckg\(^{-1}\) and was \(\dfrac{1}{1800}\) times smaller than the charge to mass ratio of the proton. The number was also the same regardless of the metal cathode used, thus Thomson determined this particle was a fundamental constitute of all matter. 
  • Therefore, the statement is true as the observations and experiment undertaken by Thomson using the interactions of particles and fields led to a greater understanding of the electrons. 

Chadwick’s Experiment:

  • In Chadwick’s experiment, he irradiated beryllium with alpha particles which emitted a deeply penetrating radiation with neutral charge. When this particle was directed into paraffin wax, protons were emitted and detected on a screen. 
  • Using the Laws of conservation of energy and momentum, Chadwick proposed the idea of a neutral particle and named it the neutron. He determined that the mass of this particle must be slightly greater than the mass of the proton.
  • Therefore, Chadwick’s observations of the neutrons led to a greater understanding of the properties of the particle, thus justifying the statement above.  

Observations using particle accelerators:

  • Particle accelerators have led to many new scientific discoveries as a result of the interaction of particles with fields and particle-particle interactions.
  • Scientists have come to a greater understanding of quarks and other subatomic particles within the standard model of matter and processes of the physical world including decay trails and momentum dilation.
  • The Large Hadron Collider (LHC) can accelerate particles close to the speed of light using electric and magnetic fields. When particles collide, the kinetic energy is converted into mass using Einstein’s equation  \(E=mc^2\).
  • The new particles formed as a result of these collisions led to the development of the standard model and increased scientific understanding of subatomic particles including up and down quarks, W/Z bosons and the Higgs Boson.
  • These subatomic particles have very short lifetimes before decaying into more stable particles. Our knowledge of them is primarily from studying their decay properties which has led to a greater understanding of particle decay trails.
  • Observations of interactions within particles accelerators has also increased the scientific understanding of momentum dilation. As particles reach relativistic speeds, a greater force is required to accelerate them than classical physics predicts which is due to mass and momentum dilation. 

Other Answers could include:

  • Millikan’s Oil drop experiment.
  • The photoelectric effect.
  • Geiger Marsden experiment.
  • Davisson Germer experiment.
  • Observations of Muons.
Show Worked Solution

One (of many) exemplar responses.

Thomson’s Experiment:

  • Thomson’s experiment tested the interaction of cathode rays (which he discovered were negatively charged subatomic particles and named them electrons) with electric and magnetic fields to determine the charge to mass ratio (\(\dfrac{q}{m}\)) of the electrons.
  • Using both the electric and magnetic fields, Thomson balanced the forces to ensure the cathode rays travelled through undeflected. Thus:
  •    \(F_E = F_B \ \ \Rightarrow \ \ qE=qvB \ \ \Rightarrow \ \ v=\dfrac{E}{B}\)
  • Using the magnetic field and known velocity, the cathode rays travelled in a circular path due to their negative charges interacting with the magnetic field. Thus:
  •    \(F_c=F_B\ \ \Rightarrow \ \ \dfrac{mv^2}{r}=qvB \ \ \Rightarrow \ \ \dfrac{q}{m}=\dfrac{v}{Br}\)
  • The charge to mass ratio was determined to be 0.77 \(\times\) 10\(^{11}\) Ckg\(^{-1}\) and was \(\dfrac{1}{1800}\) times smaller than the charge to mass ratio of the proton. The number was also the same regardless of the metal cathode used, thus Thomson determined this particle was a fundamental constitute of all matter. 
  • Therefore, the statement is true as the observations and experiment undertaken by Thomson using the interactions of particles and fields led to a greater understanding of the electrons.

Chadwick’s Experiment:

  • In Chadwick’s experiment, he irradiated beryllium with alpha particles which emitted a deeply penetrating radiation with neutral charge. When this particle was directed into paraffin wax, protons were emitted and detected on a screen. 
  • Using the Laws of conservation of energy and momentum, Chadwick proposed the idea of a neutral particle and named it the neutron. He determined that the mass of this particle must be slightly greater than the mass of the proton.
  • Therefore, Chadwick’s observations of the neutrons led to a greater understanding of the properties of the particle, thus justifying the statement above.  

Observations using particle accelerators:

  • Particle accelerators have led to many new scientific discoveries as a result of the interaction of particles with fields and particle-particle interactions.
  • Scientists have come to a greater understanding of quarks and other subatomic particles within the standard model of matter and processes of the physical world including decay trails and momentum dilation.
  • The Large Hadron Collider (LHC) can accelerate particles close to the speed of light using electric and magnetic fields. When particles collide, the kinetic energy is converted into mass using Einstein’s equation  \(E=mc^2\).
  • The new particles formed as a result of these collisions led to the development of the standard model and increased scientific understanding of subatomic particles including up and down quarks, W/Z bosons and the Higgs Boson.
  • These subatomic particles have very short lifetimes before decaying into more stable particles. Our knowledge of them is primarily from studying their decay properties which has led to a greater understanding of particle decay trails.
  • Observations of interactions within particles accelerators has also increased the scientific understanding of momentum dilation. As particles reach relativistic speeds, a greater force is required to accelerate them than classical physics predicts which is due to mass and momentum dilation. 

Other Answers could include:

  • Millikan’s Oil drop experiment.
  • The photoelectric effect.
  • Geiger Marsden experiment.
  • Davisson Germer experiment.
  • Observations of Muons.
♦♦ Mean mark 45%.

PHYSICS, M8 EQ-Bank 25

An experiment was conducted to model Millikan's oil drop experiment. In the experiment, different numbers of dominoes were placed inside seven identical boxes. The boxes were then sealed and weighed. The table shows the mass of each sealed box and some preliminary analysis.
 

Analyse this experiment to assess its effectiveness in modelling Millikan's oil drop experiment.   (6 marks)

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Overview Statement

  • The domino experiment models key components of Millikan’s method. It demonstrates how a fundamental unit is discovered through mass differences and the experimental assumptions involved.

Mass Measurement and Fundamental Unit

  • The smallest mass difference (4.3 g) represents the fundamental unit, like Millikan’s elementary charge.
  • All other mass differences are multiples of this base value, which is similar to Millikan’s findings where the value of the charge of an oil drop was always an integer multiple of `1.6 xx10^(-19)  text{C}`
  • This pattern reveals that objects contain whole numbers of a basic unit.
  • In this way, both experiments found indivisible units through mathematical patterns.

Experimental Method and Limitations

  • Unknown domino numbers parallel Millikan’s unknown electron counts on oil drops.
  • Multiple measurements enable statistical confidence in the fundamental value.
  • The assumption that 4.3 g equals one domino reflects Millikan’s assumption about single electrons.
  • Uncertainty about measuring single units affects both experiments’ reliability.
  • This similarity shows how both experiments require repeated trials to verify results.

Implications and Synthesis

  • The model effectively demonstrates Millikan’s analytical method for finding fundamental quantities.
  • Complementary experimental components work together: mass differences reveal patterns while multiple trials confirm values.
  • The experiment illustrates both strengths and weaknesses of Millikan’s approach.
Show Worked Solution

Overview Statement

  • The domino experiment models key components of Millikan’s method. It demonstrates how a fundamental unit is discovered through mass differences and the experimental assumptions involved.

Mass Measurement and Fundamental Unit

  • The smallest mass difference (4.3 g) represents the fundamental unit, like Millikan’s elementary charge.
  • All other mass differences are multiples of this base value, which is similar to Millikan’s findings where the value of the charge of an oil drop was always an integer multiple of `1.6 xx10^(-19)  text{C}`
  • This pattern reveals that objects contain whole numbers of a basic unit.
  • In this way, both experiments found indivisible units through mathematical patterns.

Experimental Method and Limitations

  • Unknown domino numbers parallel Millikan’s unknown electron counts on oil drops.
  • Multiple measurements enable statistical confidence in the fundamental value.
  • The assumption that 4.3 g equals one domino reflects Millikan’s assumption about single electrons.
  • Uncertainty about measuring single units affects both experiments’ reliability.
  • This similarity shows how both experiments require repeated trials to verify results.

Implications and Synthesis

  • The model effectively demonstrates Millikan’s analytical method for finding fundamental quantities.
  • Complementary experimental components work together: mass differences reveal patterns while multiple trials confirm values.
  • The experiment illustrates both strengths and weaknesses of Millikan’s approach.

PHYSICS, M8 EQ-Bank 27

Explain how the analysis of quantitative observations contributed to the development of the concept that certain matter and energy are quantised.   (9 marks)

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Experiments such as Millikan’s oil drop experiment and others testing the photoelectric effect have demonstrated that certain quantities of matter and energy are quantised which means they are multiples of some fundamental value.

Millikan’s Oil Drop Experiment

  • Millikan’s oil drop experiment was able to show that charge is quantised. 
  • Millikan levitated oil drops in an electric field by balancing the electric and gravitational forces on them. This allowed him to find the electric force acting on each oil drop, and using the mass of the oil drop he found its charge.
  • Analysing his results, he found that the charge on every oil drop was an integer multiple of `1.602 xx10^(-19) C`. This was determined to be the fundamental charge on an electron.
  • Further, with Thompson’s later discovery of the charge to mass ratio of an electron, its mass could be determined. 

Photoelectric Effect

  • Photoelectric effect experiments showed the quantum properties of light which seemingly contradicted the view of light as a wave.
  • It was found that there was a minimum frequency (energy) of light that would cause photoemission when it was incident upon a metal plate, and no photoemission occurred with light lower than this frequency, regardless of intensity.
  • As one photon would strike one electron on the metal surface, the electron would receive a discrete amount of energy from that photon determined by its frequency `E=hf`. If a photon didn’t have enough energy, an electron couldn’t be removed.
  • This experimental evidence changed the conceptual understanding of energy within physics and provided a basis for the quantisation of the energy of light. 

Other quantitative experiments that could be explored include:

  • Bohr’s analysis of emission spectra to demonstrate the existence of quantised energy levels in atoms.
  • Cathode ray experiments showing the particle nature of electrons.
  • Blackbody radiation experiments. 
Show Worked Solution

Experiments such as Millikan’s oil drop experiment and others testing the photoelectric effect have demonstrated that certain quantities of matter and energy are quantised which means they are multiples of some fundamental value.

Millikan’s Oil Drop Experiment

  • Millikan’s oil drop experiment was able to show that charge is quantised. 
  • Millikan levitated oil drops in an electric field by balancing the electric and gravitational forces on them. This allowed him to find the electric force acting on each oil drop, and using the mass of the oil drop he found its charge.
  • Analysing his results, he found that the charge on every oil drop was an integer multiple of `1.602 xx10^(-19) C`. This was determined to be the fundamental charge on an electron.
  • Further, with Thompson’s later discovery of the charge to mass ratio of an electron, its mass could be determined. 

Photoelectric Effect

  • Photoelectric effect experiments showed the quantum properties of light which seemingly contradicted the view of light as a wave.
  • It was found that there was a minimum frequency (energy) of light that would cause photoemission when it was incident upon a metal plate, and no photoemission occurred with light lower than this frequency, regardless of intensity.
  • As one photon would strike one electron on the metal surface, the electron would receive a discrete amount of energy from that photon determined by its frequency `E=hf`. If a photon didn’t have enough energy, an electron couldn’t be removed.
  • This experimental evidence changed the conceptual understanding of energy within physics and provided a basis for the quantisation of the energy of light. 

Other quantitative experiments that could be explored include:

  • Bohr’s analysis of emission spectra to demonstrate the existence of quantised energy levels in atoms.
  • Cathode ray experiments showing the particle nature of electrons.
  • Blackbody radiation experiments. 

PHYSICS, M8 EQ-Bank 5 MC

In an experiment, an electrically charged oil drop was suspended in air by an electric field. The electric field could be adjusted to balance the weight of the oil drop.

If more drops were suspended and measurements taken, which of the following properties would all of the oil drops be observed to have in common?

  1. The mass of each drop would be a multiple of a fundamental mass.
  2. The mass of each drop would be the same as each of the other drops.
  3. The charge of each drop would be a multiple of a fundamental charge.
  4. The charge of each drop would be the same as each of the other drops.
Show Answers Only

`C`

Show Worked Solution
  • Each oil drop would have an integer number of electrons.
  • Therefore, the charge on an oil drop would be a multiple of the charge on an electron which is a fundamental charge.

`=>C`

PHYSICS, M8 EQ-Bank 4 MC

Which of the following is true in relation to Millikan's oil drop experiment?

\begin{align*}
\begin{array}{l}
\rule{0pt}{2.5ex} \ \rule[-1ex]{0pt}{0pt}& \\
\rule{0pt}{2.5ex}\textbf{A.}\\
\text{}\rule[-1ex]{0pt}{0pt}&\text{}\\
\rule{0pt}{2.5ex}\textbf{B.}\\
\text{}\rule[-1ex]{0pt}{0pt}&\text{}\\
\rule{0pt}{2.5ex}\textbf{C.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{D.}\rule[-1ex]{0pt}{0pt}\\
\end{array}
\begin{array}{|l|l|}
\hline
\rule{0pt}{2.5ex}\textit{Aim of the experiment}\rule[-1ex]{0pt}{0pt}& \textit{Type of field used in experiment} \\
\hline
\rule{0pt}{2.5ex}\text{Measure the charge-to-mass} &\text{Electric and magnetic}\\
\text{ratio of electrons}\rule[-1ex]{0pt}{0pt}&\text{}\\
\hline
\rule{0pt}{2.5ex}\text{Measure the charge-to-mass} & \text{Magnetic}\\
\text{ratio of electrons}\rule[-1ex]{0pt}{0pt}&\text{}\\
\hline
\rule{0pt}{2.5ex}\text{Measure the charge of electrons}\rule[-1ex]{0pt}{0pt}& \text{Electric and magnetic} \\
\hline
\rule{0pt}{2.5ex}\text{Measure the charge of electrons}\rule[-1ex]{0pt}{0pt}& \text{Electric} \\
\hline
\end{array}
\end{align*}

Show Answers Only

\(D\)

Show Worked Solution
  • Millikan’s experiment involved levitating oil drops in an electric field in order to measure the charge on an electron.

\(\Rightarrow D\)

PHYSICS, M8 2019 HSC 32

Describe how specific experiments have contributed to our understanding of the electron and ONE other fundamental particle.   (5 marks)

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Millikan’s Oil Drop Experiment:

  • Millikan’s oil drop experiment involved first measuring the terminal velocity of charged oil droplets in a gravitational field and calculating their mass.
  • An electric field was applied to balance the gravitational field, allowing Millikan to find the electric force and hence, charge on an oil droplet.
  • This allowed him to find the charge on an electron as the smallest difference in charges between two oil drops.

Linear accelerator experiment discovering quarks:

  • An experiment involved using a linear accelerator to speed up and fire a beam of electrons at protons. The scattering pattern of the electrons was analysed and was consistent with protons having an internal structure with both positive and negative charges.
  • This contributed to our understanding of the existence of quarks. 

Other possible answers could include:

  • Thomson’s experiment showing the mass to charge ratio of an electron.
  • Experiments involving synchrotrons discovering particles predicted by the standard model of matter, such as the Higgs-Boson.
Show Worked Solution

Millikan’s Oil Drop Experiment:

  • Millikan’s oil drop experiment involved first measuring the terminal velocity of charged oil droplets in a gravitational field and calculating their mass.
  • An electric field was applied to balance the gravitational field, allowing Millikan to find the electric force and hence, charge on an oil droplet.
  • This allowed him to find the charge on an electron as the smallest difference in charges between two oil drops.

Linear accelerator experiment discovering quarks:

  • An experiment involved using a linear accelerator to speed up and fire a beam of electrons at protons. The scattering pattern of the electrons was analysed and was consistent with protons having an internal structure with both positive and negative charges.
  • This contributed to our understanding of the existence of quarks. 

Other possible answers could include:

  • Thomson’s experiment showing the mass to charge ratio of an electron.
  • Experiments involving synchrotrons discovering particles predicted by the standard model of matter, such as the Higgs-Boson.

♦♦ Mean mark 43%.

PHYSICS, M8 2021 HSC 23

Describe how Millikan and Thomson each used fields to determine properties of the electron.   (4 marks)

Show Answers Only

Thomson used an electric field to accelerate electrons. He deflected these electrons using a magnetic field then balanced the force on these electrons using a second electric field, allowing him to calculate the charge to mass ratio of an electron.

Millikan used electric fields to suspend oil droplets by balancing their weight due to Earth’s electric field, allowing him to calculate the charge of an electron.

Show Worked Solution

Thomson used an electric field to accelerate electrons. He deflected these electrons using a magnetic field then balanced the force on these electrons using a second electric field, allowing him to calculate the charge to mass ratio of an electron.

Millikan used electric fields to suspend oil droplets by balancing their weight due to Earth’s electric field, allowing him to calculate the charge of an electron.