Physics 3

Physics 3

1. Radiation in treatment and medicine

   • 1.1 Demonstrate an understanding of the methods that medical physicists can employ to help doctors solve medical problems, including: a CAT scans b ultrasounds c endoscopes d ionising and non-ionising radiation
   • 1.2 Use the word ‘radiation’ to describe any form of energy originating from a source, including both waves and particles
   • 1.3 Demonstrate an understanding that the intensity of radiation will decrease with distance from a source and according to the nature of the medium through which it is travelling
   • 1.4 Use the equation: intensity power of incident radiation / area
   • 1.5 Describe the refraction of light by converging and diverging lenses
   • 1.6 Relate the power of a lens to its shape
   • 1.7 Use the equation: power of lens (dioptre, D)= 1/focal length (metre, m)
   • 1.8 Investigate variations of image characteristics with objects at different distances from a converging lens
   • 1.9 Use the lens equation: 1/f = 1/u + 1/v (f=focal length (m), u = object distance (m), v =image distance (m)) The use of the real is positive sign convention is preferred and will be used in the exam
   • 1.10 Identify the following features in a diagram of the eye – cornea, iris, pupil, lens, retina, ciliary muscles
   • 1.11 Demonstrate an understanding that light is focused on the retina by the action of the lens and cornea
   • 1.12 Recall that the average adult human eye has a near point at about 25 cm and a far point at infinity
   • 1.13 Explain the symptoms and causes of short sight and long sight (students will not be expected to draw scaled ray diagrams, but may be expected to interpret them)
   • 1.14 Compare and contrast treatments for short sight and long sight, including the use of: a simple lenses b contact lenses c laser correction (combined lens equation is not required; students will not be expected to draw scaled ray diagrams, but may be expected to interpret them)
   • 1.15 Explain, with the aid of ray diagrams, reflection, refraction and total internal reflection (TIR), including the law of reflection and critical angle
   • 1.16 Calculate critical angle using Snell’s Law
   • 1.17 Explain refraction in terms of change of speed of radiation
   • 1.18 Investigate the critical angle for perspex/air or glass/air or water/air boundaries
   • 1.19 Investigate TIR between different media
   • 1.20 Explain how TIR is used in optical fibres
   • 1.21 Explain uses of optical fibres in endoscopes
   • 1.22 Explain uses of ultrasound in diagnosis and treatment

2. X-rays and ECGs

   • 2.1 Relate the ionisation by X-rays to their frequency and energy qualitatively (E=hf is not required
   • 2.2 Explain the key features of passing a current through an evacuated tube, including: a thermionic emission of electrons from a heated filament b potential difference between the cathode (filament) and the anode (metal target) c why the vacuum is necessary d possible production of X-rays by collision with a metal target
   • 2.3 Explain why a beam of charged particles is equivalent to an electric current
   • 2.4 Use the equation: current (ampere, A) = number of particles per second (1/ second, 1/s) X charge on each particle (coulomb, C)
   • 2.5 Use the equation: kinetic energy (joule, J) = electronic charge (coulomb, C) X accelerating potential difference (volt, V)
   • 2.6 Demonstrate an understanding of the inverse square law for electromagnetic radiation
   • 2.7 Relate the absorption of X-rays to the thickness of the material through which they are travelling, quantitatively
   • 2.8 Describe how X-rays are used in CAT scans and fluoroscopes
   • 2.9 Demonstrate an understanding of the comparison of the risks and advantages of using X-rays for treatment and diagnosis
   • 2.10 Explain how action potentials can be measured with an electrocardiogram (ECG) to monitor heart action
   • 2.11 Relate the characteristic shape of a normal ECG to heart action
   • 2.12 Use the equation: frequency (hertz, Hz) = 1/time period (second, s)
   • 2.13 Describe the use of a pacemaker to regulate the heart action
   • 2.14 Describe the principles and use of pulse oximetry

3. Production, uses and risks of ionising radiation from radioactive sources

   • 3.1 Evaluate the social and ethical issues relating to the use of radioactive techniques in medical physics
   • 3.2 Describe the properties of alpha, beta, gamma, positron and neutron radiation
   • 3.3 Recall the relative masses and relative electric charges of protons, neutrons, electrons and positrons
   • 3.4 Recall that in an atom the number of protons equals the number of electrons
   • 3.5 Describe the process of β- decay (a neutron becomes a proton plus an electron)
   • 3.6 Describe the process of β+ decay (a proton becomes a neutron plus a positron)
   • 3.7 Explain the effects on the atomic (proton) number and mass (nucleon) number of radioactive decays (α,β and γ decay)
   • 3.8 Use given data to balance nuclear equations
   • 3.9 Describe the features of the N-Z curve for stable isotopes
   • 3.10 Identify isotopes as radioactive from their position relative to the stability curve
   • 3.11 Recall that nuclei with high values of Z (above 82) usually undergo alpha decay
   • 3.12 Recall that an isotope above the curve has too many neutrons to be stable and will undergo beta minus decay
   • 3.13 Recall that an isotope below the curve has too many protons to be stable and will undergo Beta plus decay
   • 3.14 Recall that the proton and neutron each contain three particles called quarks
   • 3.15 Describe the arrangement of up and down quarks in protons and neutrons
   • 3.16 Use given data to explain the arrangement of up and down quarks in protons and neutrons in terms of charge and mass
   • 3.17 Explain beta minus decay as a process that involves a down quark changing into an up quark (a neutron becomes a proton and an electron)
   • 3.18 Explain beta plus decay as a process that involves an up quark changing into a down quark (a proton becomes a neutron and a positron)
   • 3.19 Recall that nuclei that have undergone radioactive decay often undergo nuclear rearrangement with a loss of energy as gamma radiation
   • 3.20 Describe the dangers of ionising radiation in terms of tissue damage and possible mutations
   • 3.21 Explain the precautions taken to ensure the safety of people exposed to radiation, including limiting the dose for patients and the risks to medical personnel
   • 3.22 Compare and contrast the treatment of tumours using radiation applied internally or externally
   • 3.23 Describe palliative care including the use of radiation in some instances
   • 3.24 Explain some of the uses of radioactive substances in diagnosis of medical conditions, including PET scanners and tracers
   • 3.25 Explain why isotopes used in PET scanners have to be produced nearby

4. Motion of particles

   • 4.1 Discuss how instruments, including particle accelerators, can help scientists develop better explanations about the physical world
   • 4.2 Discuss reasons for collaborative, international research into big scientific questions, including particle physics
   • 4.3 Explain how for motion in a circle there must be a resultant force known as a centripetal force that acts towards the centre of the circle
   • 4.4 Explain how particle accelerators called cyclotrons cause charged particles to move in a circular or spiral path, due to a magnetic field
   • 4.5 Demonstrate an understanding that certain stable elements can be bombarded with proton radiation to change them into radioactive isotopes
   • 4.6 Describe the use of particle accelerators (cyclotrons) to produce radioactive isotopes for medical purposes
   • 4.7 Demonstrate an understanding that for inelastic collisions momentum is conserved but kinetic energy is not conserved
   • 4.8 Demonstrate an understanding that for elastic collisions both momentum and kinetic energy are conserved
   • 4.9 Analyse collisions in one dimension in terms of momentum and kinetic energy
   • 4.10 Carry out calculations using momentum conservation for a two-body collision (in one dimension only)
   • 4.11 Carry out calculations using conservation of kinetic energy for a two-body elastic collision (in one dimension only)
   • 4.12 Investigate factors affecting the height of rebound of bouncing balls
   • 4.13 Recall that gamma rays can be produced by the annihilation of an electron and a positron
   • 4.14 Apply conservation of momentum and charge to positron electron annihilation
   • 4.15 Apply the idea of conservation of mass energy for positron electron annihilation a) in a qualitative way (calculations involving E=mc² will not be required) b) in a quantitive way using the equation E=mc²
   • 4.16 Explain the use of radio isotopes in PET scanners to produce gamma rays

5. Kinetic theory and gases

   • 5.1 Use a simple kinetic theory model to describe movement of particles in the three states of matter
   • 5.2 Explain the pressure of a gas in terms of the motion of its particles
   • 5.3 Describe the effect of changing the temperature of a gas on the speed of its particles
   • 5.4 Describe the term absolute zero, -273°C, in terms of the lack of movement of particles
   • 5.5 Convert between the Kelvin and Celsius scales
   • 5.6 Recall that the average kinetic energy of the particles in a gas is directly proportional to the Kelvin temperature of the gas
   • 5.7 Investigate the temperature and volume relationship for a gas
   • 5.8 Use the relationship: V1=V2 T1/T2 to calculate volume for gases of fixed mass at constant pressure (rearranging not required)
   • 5.9 Investigate the volume and pressure relationship for a gas
   • 5.10 Use the relationship: V1P1=V2P2 to calculate volume or pressure for gases of fixed mass at constant temperature
   • 5.11 Use the equation: initial pressure (pascal, Pa) X initial volume (metre3, m3) / initial temperature (kelvin, K) = final pressure (pascal, Pa) X final volume (metre3, m3) / final temperature (kelvin, K) P1V1/T1=P2V2/T2
   • 5.12 Apply an understanding of the equation in 5.11 to the use of bottled gases in medicine, including the need for a pressure above atmospheric and the calculation of the volume of gas released at atmospheric pressure