P4: Radiation For Life Revision List

GCSE Physics P4 (OCR B722): Radiation for Life

Year 11 revision topics for the OCR GCSE Physics P4 specification

P4: Radiation For Life Revision List

October 22, 2017 admin

P4a Sparks

  • Recognise that when some materials are rubbed they attract other objects:
    • certain types of dusting brushes become charged and attract dust as they pass over it.

 

  • Recognise that insulating materials can become charged when rubbed with another insulating material.
  • Be able to state that there are two kinds of electric charge:
    • positive
    • negative.

 

  • Be able to describe how you can get an electrostatic shock from charged objects
    • eg synthetic clothing.
  1. Be able to describe how you can get an electrostatic shock if you become charged and then become earthed
    • eg touching water pipes after walking on a floor covered with an insulating material like synthetic carpet.

 

  • Know that like charges repel and unlike charges attract.
  • Understand that electrostatic phenomena are caused by the transfer of electrons, which have a negative charge.

 

  • Be able to describe static electricity in terms of the movement of electrons:(HT)
    • a positive charge due to lack of electrons
    • a negative charge due to an excess of electrons.

 

  • Know that atoms or molecules that have become charged are called ions.(HT)
  • Be able to explain how static electricity can be dangerous when:
    • in atmospheres where explosions could occur eg inflammable gases or vapours or with high concentrations of oxygen
    • in situations where large quantities of charge could flow through the body to earth.

 

  • Be able to explain how static electricity can be a nuisance:
    • dirt and dust attracted to insulators (plastic containers, TV monitors etc)
    • causing clothing to ‘cling’.

 

  • Be able to explain how anti-static sprays, liquids and cloths help reduce the problems of static electricity. (HT)
  • Be able to explain how the chance of receiving an electric shock can be reduced by:(HT)
    • correct earthing
    • use of insulating mats
    • using shoes with insulating soles
    • bonding fuel tanker to aircraft.

 

P4b Uses of electrostatics

  • Know that electrostatics can be useful for electrostatic precipitators:
    • remove the dust or soot in smoke
    • used in chimneys.

 

  • Know that electrostatics can be useful for spraying:
    • spray painting
    • crop spraying

 

  • Know that electrostatics can be useful for restarting the heart when it has stopped (defibrillator).
  • Know that defibrillators work by discharging charge.
  • Be able to explain how static electricity can be useful for electrostatic dust precipitators to remove smoke etc from chimneys:
    • dust passes through charged metal grid or past charged rods
    • dust particles become charged
    • plates are earthed or charged opposite to grid
    • dust particles are attracted to the plates.
    • plates struck and dust falls to collector

 

  • Be able to explain how static electricity is used in electrostatic dust precipitators to remove smoke particles etc from chimneys:(HT)
    • high voltage metal grids put into chimneys to produce a charge on the dust
    • dust particles gain or lose electrons
    • dust particles induce a charge on the earthed metal plate
    • dust particles attracted to the charged plates

 

  • Be able to explain how static electricity can be useful for paint spraying:
    • spray gun charged
    • paint particles charged the same so repel giving a fine spray and coat
    • object charged oppositely to paint so attracts paint into the ‘shadows’ of the object giving an even coat with less waste.

 

  • Be able to explain how static electricity is used in paint spraying, in terms of paint and car gaining and losing electrons and the resulting effects(HT)
  • Be able to explain how static electricity can be useful for restarting the heart when it has stopped (defibrillator):
    • paddles charged
    • good electrical contact with patient’s chest
    • charge passed through patient to make heart contract
    • care taken not to shock operator.

 

P4c: Safe electricals

  • Be able to explain the behaviour of simple circuits in terms of the flow of electric charge.
  • Be able to describe and recognise how resistors can be used to change the current in a circuit.

 

  • Be able to describe how variable resistors can be used to change the current in a circuit:
    • longer wires give less current
    • thinner wires give less current (rheostat configured as a variable resistor only).

 

  • Know that resistance is measured in ohms.
  • Know the colour coding for live, neutral and earth wires:
    • live – brown
    • neutral – blue
    • earth – green/yellow.

 

  • Know and understand that ‘double insulated’ appliances do not need earthing.
  • Be able to describe reasons for the use of fuses and circuit breakers (as re-settable fuses).
  • Know that an earthed conductor cannot become live.
  • Be able to explain how variable resistors can be used to change the current in a circuit:
    • longer wires have more resistance
    • thinner wires have more resistance (rheostat configured as a variable resistor only).

 

  • Be able to describe the relationships between current, voltage (pd) and resistance:
    • for a given resistor, current increases as voltage increases and vice versa
    • for a fixed voltage, current decreases as resistance increases and vice versa.

 

  • Be able to use the equation: resistance = voltage / current
  • Be able to use and apply the equation, including a change of subject:(HT)
    • resistance (R) = voltage(V) / current (I)
    • eg R = V/I, V = IR and I = V/R

 

  • Be able to describe the functions of the live, neutral and earth wires:
    • live – carries the high voltage
    • neutral – completes the circuit
    • earth – a safety wire to stop the appliance becoming live.

 

  • Be able to explain how a wire fuse reduces the risk of fire; if the appliance develops a fault:
    • too large a current causes the fuse to melt
    • preventing flow of current
    • prevents flex overheating and causing fire
    • prevents further damage to appliance.

 

  • Be able to use the equation: power = voltage × current
  • Be able to explain why ‘double insulated’ appliances do not need earthing:
    • the appliance is a non conductor and cannot become live.

 

  • Be able to explain how the combination of a wire fuse and earthing protects people.(HT)
  • Be able to explain the reasons for the use of fuses and circuit breakers as re-settable fuses (structure and mode of operation not required).(HT)
  • Use the equation, including a change of subject:
    • power (P) = voltage (V) × current (I)
    • to select a suitable fuse for an appliance.
    • P = IV, V = P/I and I = P/V

 

P4d Ultrasound

  • Suggested practical and research activities to revise from
    • Looking at ultrasound pictures and investigate the hearing range of pupils in the class.
    • Investigating the properties of longitudinal waves.
    • Use a slinky and/or rope to demonstrate wave behaviours.
    • Use echoes from hard surfaces to develop the idea of reflection of sound, and calculation of distance surface (using the echo time and speed of sound).

 

  • Know that ultrasound is a longitudinal wave.
  • Recognise features of a longitudinal wave:
    • wavelength
    • compression
    • rarefaction.

 

  • Recognise that ultrasound can be used in medicine to the for diagnostic purposes:
    • to look inside people by scanning the body
    • to measure the speed of blood flow in the body
    • (You are not expected to describe the Doppler effect).

 

  • Be able to describe features of longitudinal waves:
    • wavelength
    • frequency
    • compression (a region of higher pressure)
    • rarefaction (a region of lower pressure).

 

  • Be able to describe and compare the motion and arrangement of particles in longitudinal and transverse physical waves:(HT)
    • wavelength, frequency , compression , rarefaction , amplitude.

 

  • Know that the frequency of ultrasound is higher than the upper threshold of human hearing (20 000 Hz) because the ear cannot detect these very high frequencies.
  • Know that ultrasound can be used in medicine for non-invasive therapeutic purposes such as to break down kidney and other stones.

 

  • Be able to explain how ultrasound is used in:(HT)
    • body scans (reflections from different layers returning at different times from different depths)
    • breaking down accumulations in the body such as kidney stones.

 

  • Be able to explain the reasons for using ultrasound rather than X-rays for certain scans:(HT)
    • able to produce images of soft tissue
    • does not damage living cells.

 

P4e: Radioactivity

  • Know that the radioactivity or activity of an object is measured by the number of nuclear decays emitted per second.
  • Know and understand why radioactivity decreases with time.
  • Know that nuclear radiation ionises materials.
  • Know that radiation comes from the nucleus of the atom.
  • Be able to describe radioactive substances as decaying naturally and giving out nuclear radiation in the form of alpha, beta and gamma.
  • Be able to explain and use the concept of half-life.
  • Be able to interpret graphical data of radioactive decay to include a qualitative description of half-life.

 

  • Be able to explain ionisation in terms of:
    • removal of electrons from particles
    • gain of electrons by particles.

 

  • Be able to interpret graphical or numerical data of radioactive decay to include calculation of half-life.(HT)
  • Be able to explain why alpha particles are such good ionisers.(HT)
  • Be able to describe radioactivity as coming from the nucleus of an atom that is unstable.
  • Know that an alpha particle is a helium nucleus.
  • Know that a beta particle is a fast moving electron.

 

  • Be able to describe what happens to a nucleus when an alpha particle is emitted:(HT)
    • mass number decreases by 4
    • nucleus has two fewer neutrons
    • nucleus has two fewer protons
    • atomic number decreases by 2
    • new element formed.

 

  • Be able to describe what happens to a nucleus when a beta particle is emitted:(HT)
    • mass number is unchanged
    • nucleus has one less neutron
    • nucleus has one more proton
    • atomic number increases by one
    • new element formed.

 

  • Be able to construct and balance nuclear equations in terms of mass numbers and atomic numbers to represent alpha and beta decay.(HT)

P2f: Use of Radioisotopes

  • Understand why background radiation can vary.
  • Know that background radiation mainly comes from rocks and cosmic rays.

 

  • Know industrial examples of the use of tracers:
    • to track dispersal of waste
    • to find leaks/blockages in underground pipes
    • to find the route of underground pipes.

 

  • Know that alpha sources are used in some smoke detectors.
  • Know that radioactivity can be used to date rocks.
  • Know that some background radiation comes from waste products and man-made sources eg waste from:
    • industry
    • hospitals.

 

  • Be able to evaluate the relative significance of sources of background radiation.(HT)
  • Be able to describe how tracers are used in industry:
    • radioactive material put into pipe
    • progress tracked with detector above ground/outside pipe
    • leak/blockage shown by reduction/no radioactivity after the point of blockage.

 

  • Be able to explain why gamma radiation is used as an industrial tracer.(HT)
  • Be able to explain how a smoke detector with an alpha source works:
    • smoke particles hit by alpha radiation
    • less ionisation of air particles
    • current is reduced causing alarm to sound.

 

  • Be able to explain how the radioactive dating of rocks depends on the calculation of the uranium/lead ratio.
  • Know that measurements from radioactive carbon can be used to find the date of old materials.
  • Be able to explain how measurements of the activity of radioactive carbon can lead to an approximate age for different materials:(HT)
    • the amount of Carbon-14 in the air has not changed for thousands of years
    • when an object dies (eg wood) gaseous exchange with the air stops
    • as the Carbon-14 in the wood decays the activity of the sample decreases
    • the ratio of current activity from living matter to the activity of the sample is used to calculate the age within known limits.

 

P4g: Treatment

  • Be able to describe some similarities and differences between X-rays and gamma rays:
    • both are ionising electromagnetic waves
    • have similar wavelengths
    • are produced in different ways.

 

  • Know that medical radioisotopes are produced by placing materials into a nuclear reactor.
  • Be able to describe uses of nuclear radiation in medicine, to include:
    • diagnosis
    • treatment of cancer using gamma rays
    • sterilisation of equipment.

 

  • Know that only beta and gamma radiation can pass through skin.
  • Know that nuclear radiation can damage cells.
  • Be able to describe the role of a radiographer and the safety precautions they must take.
  • Know that materials absorb some ionising radiation.
  • Know and understand how the image produced by the absorption of X-rays depends on the thickness and density of the absorbing materials.

 

  • Be able to explain how:(HT)
    • gamma rays are given out from the nucleus of certain radioactive materials
    • X-rays are made by firing high speed electrons at metal targets
    • X-rays are easier to control than gamma rays.

 

  • Be able to describe how materials can become radioactive as a result of absorbing extra neutrons.
  • Be able to explain why gamma (and sometimes beta) emitters can be used as tracers in the body.
  • Understand why medical tracers should not remain active in the body for long periods.

 

  • Be able to explain how radioactive sources are used in medicine:(HT)
    1. (i) to treat cancer:
      • gamma rays focused on tumour
      • wide beam used
      • rotated round the patient with tumour at centre
      • limiting damage to non-cancerous tissue.
    2. (ii) as a tracer:
      • beta or gamma emitter with a short half life
      • drunk/eaten/ingested/injected into the body
      • allowed to spread through the body
      • followed on the outside by a radiation detector.

P2h Fision and Fusion

  • Know that nuclear power stations use uranium as a fuel.
  • Be able to describe the main stages in the production of electricity:
    • source of energy
    • used to produce steam
    • used to produce electricity.

 

  • Be able to describe the process that gives out energy in a nuclear reactor as nuclear fission, and that it is kept under control.
  • Know that nuclear fission produces radioactive waste.

 

  • Be able to describe the difference between fission and fusion:
    • fission is the splitting of nuclei – making two smaller atoms
    • fusion is the joining of nuclei – making a larger atom

 

  • Be able to explain why the claims are disputed – because other scientists could not repeat their findings.
  • Know that one group of scientists have claimed to successfully achieve ‘cold fusion’.
  • Be able to describe how domestic electricity is generated at a nuclear power station:
    • nuclear reaction
    • producing heat
    • heating water to produce steam
    • spinning a turbine
    • driving a generator.

 

  • Be able to describe what happens to allow uranium to release energy:(HT)
    • uranium nucleus hit by neutron
    • causes nucleus to split
    • energy released
    • more neutrons released.

 

  • Be able to describe a nuclear bomb as a chain reaction that has gone out of control.
  • Know how the decay of uranium starts a chain reaction.
  • Be able to explain what is meant by a chain reaction:(HT)
    • when each uranium nucleus splits more than one neutron is given out
    • these neutrons can cause further uranium nuclei to split.

 

  • Be able to explain how scientists stop nuclear reactions going out of control:(HT)
    • rods placed in the reactor
    • to absorb some of the neutrons
    • allowing enough neutrons to remain to keep the process operating.

 

  • Be able to describe how nuclear fusion releases energy:
    • fusion happens when two nuclei join together
    • fusion produces large amounts of heat energy
    • fusion happens at extremely high temperatures.

 

  • Be able to describe why fusion for power generation is difficult:
    • requires extremely high temperatures
    • high temperatures have to be safely managed.

 

  • Understand why fusion power research is carried out as an international joint venture.
  • Be able to explain how different isotopes of hydrogen can undergo fusion to form helium:(HT)
    • 11H + 21H ==> 32He

 

  • Understand the conditions needed for fusion to take place, to include:(HT)
    • in stars, fusion happens under extremely high temperatures and pressures
    • fusion bombs are started with a fission reaction which creates exceptionally high temperatures
    • for power generation exceptionally high temperatures and/or pressures are required and this combination offers (to date) safety and practical challenges.

 

  • Be able to explain why the ‘cold fusion’ experiments and data have been shared between scientists.
  • Be able to explain why ‘cold fusion’ is still not accepted as a realistic method of energy production.(HT)