"100 Things to Remember.
Q1. What is the diameter of a proton? ?10?^(-15) m
Q2. What is the extent of the visible universe? ?10?^25 m
Q3. What is the mass of an electron? ?10?^(-30) kg
Q4. What is the mass of the universe? ?10?^50 kg
Q5. How long does light take to pass a nucleus? ?10?^(-23) s
Q6. What is the age of the universe? ?10?^18 s
Q7. State the 6 fundamental units in the SI system. m, kg, s, ampere, mole, K
Q8. The effect of which type of error is reduced by repeated measurement?
Q9. What is the difference between
accuracy (how close a measurement is to the accepted value) and
precision (the agreement among a number of measurements made in the same way)?
Q10. What is the difference between instantaneous and average velocity? Slope of tangent versus slope of chord of displacement time graph
Q11. What is the difference between linear and proportional (passes through the origin) graphs?
Q11. What two conditions are necessary before you can apply the kinematic equations? Straight line motion and constant acceleration
Q12. What forces act on an object travelling at terminal velocity?
Weight and fluid resistance
Q13. What does the area under a velocity-time graph represent? Displacement
Q14. What does the slope of a velocity-time graph represent? Acceleration
Q15. State Newton’s First Law of Motion.
Every object travels in a straight line at constant speed or remains at rest, unless acted upon by a net external force.
Q16. State the condition for translational equilibrium. No net force
Q17. State Newton’s Second Law of Motion.
Net force equals rate of change of momentum
Q18. State the Law of Conservation of Linear Momentum.
In a closed system, momentum is conserved in all collisions.
Q19. State Newton’s Third Law of Motion.
"For every action there is an equal and opposite reaction."
IB wants … "When a force acts on a body an equal and opposite force acts on the other body"
Q20. What does the area under a force-displacement graph represent? Work done
Q21. State the law of conservation of energy.
Energy cannot be created or destroyed, it merely changes form.
Q22. What is the difference between an elastic and an inelastic collision?
Energy is conserved in an elastic collision.
Q23. Define power. Rate of using energy or rate of doing work
Q24. Define efficiency. Work out compared to energy in
Q25. What can be said about the acceleration of an object describing uniform circular motion?
Constant, towards centre of circle
Q26. What determines the direction of thermal energy transfer between objects?
Q27. What is the relationship between the Kelvin and Celsius scales of temperature? C + 273 = K
Q28. What is the internal energy of a substance?
Total potential energy and random kinetic energies
Q29. List three thermal macroscopic concepts.
Temperature, internal energy, thermal energy (heat) … " heat is a non-mechanical transfer of energy"
Q30. Define heat capacity of an object.
Energy required to raise temperature by one K
Q31. Define specific heat capacity.
Energy required, per kilogram, to raise temperature by one K
Q32. What is the change of phase from gas to liquid called?
Q33. Distinguish between evaporation and boiling. Evaporation occurs below boiling point, and only at the surface. Boiling occurs at a constant temperature.
Q34. Define specific latent heat.
energy per unit mass absorbed or released during a phase change
Q35. Define pressure. force per unit area acting on a surface
Q36. State the defining equation of SHM.? a= -??^2 x (?=2pf)
Q37. State what is meant by damping. When a force is always in the opposite direction to the direction of motion of the oscillating particle (NOTE: this force is a dissipative force)
Q38. State what is meant by resonance. a transfer of energy in which an oscillating force matches the natural frequency of the system resulting in a large amplitude of vibration
Q39. Define wave speed. speed of transfer of the energy of the wave
Q40. List the seven principal electro-magnetic radiations from lowest to highest energy. Radio waves, microwaves, infra-red, visible, UV, X-ray, gamma rays
f: ?10?^8 Hz ?10?^10 Hz ?10?^12 Hz ?10?^14 Hz ?10?^16 Hz ?10?^18 Hz ?10?^20 Hz
Q41. State Snell’s Law. For any two media the ratio of sin i to sin r is a constant
Q41A. State the principle of superposition. When pulses and waves (unlike particles) cross …
the net displacement of the medium (through which waves travel)
is equal to the vector sum of the individual displacements.
Q42B. Coherent light sources have a constant phase difference, and the same wavelength.
Q42. What is a force field? … "a region in space where an object will experience a force due its charge or mass."
Q42. Define electric potential difference. Work per unit charge needed to move a charge from one point to another.
Q43. Define the electronvolt. The energy an object with the charge of one electron acquires after being accelerated through a PD of one volt.
Q44. Define Ohm’s Law. The current flowing through a device is proportional to the potential difference applied across it providing the temperature is constant. (NOTE: R = V/I is not Ohm’s Law)
Q45. What is the resistance of an ideal voltmeter? infinite
Q46. Define gravitational field strength? gravitational force per unit mass on a point mass
Q47. State the Law of Conservation of Charge. The total electric charge of an isolated system remains constant
Q48. State Coulomb’s Law. The electric force between two point charges is directly proportional to the product of the two charges and inversely proportional to square of the distance between them, and directed along the line joining the two charges.
Q49. What is meant by a radial field? Straight lines emanating from a point.
Q50. What causes magnetic fields? Moving charges
Q51. Describe a simple model of the atom.
Electrons orbit a nucleus as a result of electrostatic attraction.
Q52. What evidence supports the nuclear model of the atom? Geiger-Marsden expt
Q53. Outline one limitation of the simple model of the nuclear atom.
Accelerating charges radiate energy … atoms collapse! (and what holds the protons together?)
Q54. Define nuclide. A member of an atomic species
Q55. Define isotopes. Atoms with same atomic number, but different mass numbers.
Q56. Define nucleon. Protons and neutrons
Q57. Describe what is meant by radioactive decay.
(i)Unstable nuclei randomly change/emit energy
(ii) by the release of alpha particles, electrons, gamma rays
Q58. Describe the ionizing properties of alpha, beta and gamma radiation.
Alpha is the most ionizing (but short range)
Q59. Outline the biological effects of ionizing radiation.
Cells can die, or mutate (if DNA is changed)
Q60. How does the rate of decay of a radioactive sample change over time?
Q61. Define radioactive half-life. The time it takes for half the nuclei in a sample to decay.
Q62. Give an example of artificial transmutation.
Q63. Define the term unified atomic mass unit.
One twelfth the mass of an atom of (_6^12)C
Q64. Define mass defect.
The difference between the mass of a nucleus, and its component nucleons.
Q65. Define binding energy.
The energy needed to completely separate the components of a nucleus.
The energy released when a nucleus is assembled from its components.
Q66. Describe nuclear fission.
Large nuclei are broken into smaller nuclei, and energy is released.
Q67. Describe nuclear fusion.
Small nuclei join together to form larger nuclei, and energy is released.
Q68. What is the main source of the sun's energy? Nuclear fusion
Q69. State the Second Law of Thermodynamics.
(i) Thermal energy may be completely converted to work in a single process, but
(ii) continuous conversion requires a cyclical process and the transfer of some energy from the system
Q70. What is meant by degraded energy?
In any process that involves energy transformations, the energy transferred to the surroundings is no longer available to do useful work.
Q71. What is the principal mechanism in production of electrical power?
Rotate coils in a magnetic field.
Q72. What is the prime source of world energy? The Sun.
Q73. Define energy density.
ratio of the energy released from the fuel to the mass of the fuel consumed
Q74. State the relative proportions of energy use.
Oil 37% Coal 27% Natural Gas 23% Nuclear 7% Hydro 7%
Q75. What are the historical and geographical reasons for the widespread usage of fossil fuels?
(i) Industrialisation led to high energy use
(ii) so industry developed near large supplies of fossil fuels
Q76. List the overall efficiencies of power stations fuelled by different fossil fuels. Natural gas 45% Oil 38% Coal 35%
Q77. Which neutrons initiate chain reactions? Low energy (1 eV)
Q78. Define critical mass.
The minimum number of fissionable nuclei in order to sustain a chain reaction.
Q78. What is fuel enrichment? Naturally occurring uranium contains less than 1% U-235.
Q79. What is the role of a moderator in a thermal fission reactor?
To slow down neutrons (fast moving neutrons pass through nuclei.)
Q80. What is the role of the control rods in a thermal fission reactor?
They absorb neutrons to control the rate of the reaction.
Q81. What is the role of the heat exchanger in a thermal fission reactor?
Water is piped through the core, so the nuclear reaction can be separated from the environment.
Q82. What is the result of neutron capture by U-238? Pu-239
Q83. What is the main problem with obtaining power from nuclear fusion?
Confining a high-temperature high-density plasma
Q84. What energy transfer occurs in a photovoltaic cell? Solar to electrical
Q85. What energy transfer occurs in a solar heating panel? Solar to thermal
Q86. What are the basic features of a wind generator?
1. Tower to support rotating blades. 2. Blades that can be rotated to face into the wind.
3. Generator. 4. Storage system or connection to a distribution grid
Q87. How does an OWC operate?
1. Wave capture chamber is set into rock face on land where waves hit the shore.
2. Tidal power forces water into a partially filled chamber that has air at the top.
3. This air is alternately compressed and decompressed by the “oscillating water column.”
4. These rushes of air drive a turbine which generates electrical energy.
Q88. Define albedo. The ratio of radiation reflected compared to incident radiation.
Q89. State factors which determine the albedo of a planet.
Cloud formation, nature of surface (ice, water, forest etc …)
Q90. Describe the greenhouse effect.
IR radiation passes through the atmosphere and warms the earth.
Longer wavelength IR is reradiated.
This radiation is absorbed by atmosphere and reradiated.
Q91. Identify the main greenhouse gases and their sources.
1. Methane (livestock, fermentation of plant matter) 2. Water
3. Carbon dioxide (burning fossil fuels, deforestation) 4. Nitrous oxide (livestock and industry)
Q92. Explain the molecular mechanism by which greenhouse gases absorb IR radiation.
The natural frequency of oscillation of greenhouse gases matches the frequency of the IR radiation. This causes resonance.
Q93. State the Stefan-Boltzmann law. P= sAT^4
Q94. Define surface heat capacity.
The energy required to raise the temperature of a unit area of a surface by one Kelvin.
Q95. What is meant by the enhanced greenhouse effect?
An increase in the greenhouse effect due to human activities.
Q96. What evidence links global warming to the enhanced greenhouse effect?
Ice core data shows a link between atmospheric ?CO?_2 and temperature.
Q97. Outline some mechanisms that may increase global warming.
Global warming reduces ice and snow cover, which in turn reduces the albedo. This will result in an increase in the overall rate of heat absorption.
Temperature increase reduces the solubility of CO2 in the sea and increases atmospheric concentrations.
Deforestation results in the release of more CO2 into the atmosphere due to “slash-and-burn” clearing techniques, as well as reduces the number of trees available to provide “carbon fixation.”
Q98. Define coefficient of volume expansion.
The ratio of change in volume per degree change, compared to original volume.
Q99. Why is difficult to predict a rise in sea-level?
Anomolous expansion of water. (Between O and 4 degrees water contracts.)
Q100. List some ways to reduce the enhanced greenhouse effect.
Advances in technology (decarbonise exhausts, increase efficiency, fusion reactors)
Reduce energy requirements
Replace use of oil and coil with renewable energy
Plant trees and protect forests
". by Baaz
Displacement Position of an object relative to its starting position.
Velocity Rate of change of displacement.
Speed Rate of change of distance.
Acceleration Rate of change of velocity.
Newton's First Law An object continues in uniform motion in a straight line/ at rest unless a resultant force acts.
Newton's Second Law The acceleration of an object is proportional to and in the same direction as its resultant force.
Newton's Third Law When 2 objects react, the exert equal and opposite forces on each other.
Linear Momentum The product of mass and velocity.
Impulse Change in momentum.
Law of conservation of momentum Momentum of object in system stays the same in a closed system.
Work Force X distance moved in direction of force.
Kinetic Energy The energy an object has due to it's motion
Change in GPE The energy an object has due to its position above the Earth.
Elastic Collision KE is conserved and objects bounce off with the same speed it did before in opposite directions.
Inelastic Collision Maximum loss of KE, objects stick together & momentum is still conserved.
Explosion Objects move away from each other, internal energy becomes KE.
Efficiency Ratio of work out: energy put in.
Mole Amount of substance that has the same number of molecules as the number of of molecules as the number of atoms in 12g of C-12.
Molar Mass Mass of 1 mole of the substance.
Avogadro's Constant Number of molecules in 1 mole = 6.022 × 10²³
Specific Heat Capacity The energy needed to increase the temperature of of 1 kilo of an object by 1K.
Thermal Capacity The energy needed to increase the temperature of an object by 1K.
Specific Latent Heat Amount of heat needed to change the state of 1 kilo of a substance WITHOUT a change in temperature.
Pressure Force per unit area.
Displacement (SHM) Distance away a particle is from its equilibrium position.
Amplitude (SHM) Maximum displacement of a particle from its equilibrium position.
Frequency (SHM) Number of oscillations produced per second.
Period (SHM) Time taken for a complete oscillation.
Phase Difference (SHM) The fraction of an oscillation that one wave moves behind another.
Simple Harmonic Motion Motion where the acceleration of an object is proportional to & in the opposite direction to displacement. a = -?2x
Damping Process where the energy of an oscillating system decreases with amplitude by a dissipative force acting in the opposite direction.
Natural frequency The frequency that a system naturally oscillates at.
Forced oscillation An oscillation that occurs & stays , Where an object is forced to oscillate by an external force.
Resonance When the frequency of a driving force matches the natural frequency of oscillation.
Transverse wave Oscillations are at 90° to direction of energy transfer/ wave motion.
Longitudinal wave Oscillations are parallel to direction of energy transfer/ wave motion.
Crest Point on a wave with maximum positive displacement.
Trough Point on a wave with maximum negative displacement.
Compression Region (on a wave) where particles are closer together than they would be in their equilibrium state.
Rarefaction Region (on a wave) where particles are further apart than they would be in their equilibrium state.
Wavelength The shortest distance between 2 points on a wave that are in phase.
Wave speed The speed at which wave fronts pass a stationary observer.
Intensity The power per unit area received by an observer from a wave.
Principle of superposition When 2 or more waves of the same type meet, the total displacement at a point on a wave is the displacements of the individual waves added at that point.
Constructive/destructive interference Phase difference is 0/ out of phase& path difference is a whole 'n' of wavelength/ a fraction of it.
Electric potential difference Work done per unit charge in moving a positive charge from one point in the (electric) field to another.
Electronvolt The amount of energy an electron gains by moving through a potential difference of 1 volt.
Electric current The rate of flow of electrical charge.
Resistance The ratio of voltage across the material to the current flowing through it.
Ohm's Law The current through a wire is proportional to the p.d. across it; as long as the temperature is constant.
Electromotive force (emf) The power supplied by the supply per unit current.
Internal resistance Resistance if a source (of power).
Gravitational field strength The force per unit mass experienced by a small test mass placed in the field.
Newton's universal law of gravitation Any point mass attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to their separation².
Electric field strength The force per unit charge experienced by a small test charge placed in the field.
Magnetic field strength F=BILsinø
Direction: 90° to field lines.
Nuclide An atom with a particular nucleus configuration.
Nucleon A proton or a neutron.
Isotope An element with the same number of protons but a different number of neutrons.
Radioactive half life The time taken for the total number of nuclei (of a radioactive substance) to halve.
Unified atomic mass The mass of ½ of the nucleus of a C-12 isotope.
Mass defect The difference in mass between a nucleus and its separate nucleons.
Binding energy per nucleon The total binding energy for the nucleus divided by the total number of nucleons
Binding energy The energy needed to break up a nucleus into its constituent nucleons.
Degraded energy Energy transferred to surroundings that can no longer do useful work.
Energy density The mean energy liberated per kg of a fuel.
Fuel enrichment A process where you increase percentage of U-235 to make fission more likely.
Moderator Slows down fast neutrons to increase the chance of more reactions. (So they don't pass through the nuclei)
Control rod This absorbs neutrons to control chain reactions.
Heat exchanger This allows the nuclear reactions to occur in a place that is sealed off from the rest of the environment. The thermal energy is transferred to heat water, and the steam that is produced turns the turbines.
Photovoltaic cell Light hits semiconductors & electrons are released/ moved; creating an electric field.
Solar heating panel Heat goes through glass pane & is absorbed by black pipes with running water in them.
Albedo The ratio of reflected: incident radiation.
Stefan- Boltzmann law Total power radiated ? T4 OR P= sAT4.
Emissivity The ratio of power emitted by a body to the power emitted if it was a black body.
Surface heat capacity The energy needed to raise the temperature of a unit area of a planet's surface by 1K.
Enhanced greenhouse effect Rising global temperatures due to greenhouse gases being put into the atmosphere because of human activities
Coefficient of volume expansion The fractional change in volume per degree change in temperature.
Gravitational potential Work done per unit mass in bringing a test mass from infinity to that point in the field.
*Gravitational potential energy Work done in moving an object from infinity to that point.
Electric potential The work done per unit charge in bringing a positive test charge from infinity to that point in the field.
Electric potential energy The work done moving a charge from infinity to a point in an electric field.
Isochoric Constant volume: no work is done.
Isobaric Constant pressure: Work done is area under line.
Isothermal Constant temperature: Work done= area under curve.
Adiabatic No heat transfer: compression/ expansion. Work is done on/ by gas
Standing waves Transfer no energy. They have the same amplitude and are in phase. Happens when a wave & its reflection interfere (or just 2 waves)
One dimensional standing wave Happens when a wave reflects back from a boundary along the route it came.
Doppler Effect The change in perceived frequency because the source or observer is moving.
Rayleigh criterion 2 points will be resolvable if the first minimum of the diffraction pattern of one source overlaps the central maximum of the diffraction pattern of the second source.
Polarized light Light with waves that vibrate in 1 plane.
Brewster's angle Happens when the transmitted ray is 90° to the reflected ray. The angle gives us the angle of incidence needed for plane-polarized light.
Polariser A device that makes polarized light from an unpolarised beam.
Analyser A polariser used to detect polarised light.
Optically active substance A substance that rotates the plane of polarisation of light that goes through it.
Stress analysis If polarised white light is shone on plastic, you can see the stress points where the coloured lines are.
Magnetic flux A measure of the strength of a magnetic field over a given area/ number of field lines.
Magnetic flux linkage The product of the magnetic flux and the number of turns in a given coil.
Faraday's law The size of an induced emf is proportional to the rate of change of flux linkage.
Lenz's law The direction of an induced current is such that it'll oppose the change causing it.
de Broglie Hypothesis All particles have a wave like nature.
Electron in a box model An electron has possible wavelengths like a standing wave on a string so electrons have discrete energies.
Schrödinger's model This gives the probability of where the electron could be (probability regions called orbitals).
Heisenberg uncertainty principle You can only know 1 from each pair:
-momentum & position
-energy & time
Decay constant Probability of decay of a nucleus per unit time
Radioactive decay law The activity of a radioactive sample ? Number of radioactive nuclei present.
Capacitance Charge per unit p.d. that can be stored on a capacitor.
Quantum efficiency The ratio of the number of photoelectrons emitted: the number of photons incident on the pixel.
Magnification The ratio of the length of the image on the CCD: the length of the object.
Stellar cluster A group of stars that are physically near each other in space.
Constellation A pattern of stars as seen from Earth that aren't physically near each other in space.
Light year The distance that light travels in 1 year.
Luminosity The total power emitted by a star.
Apparent brightness The power received per unit area on Earth by a star.
Cepheid A slightly unstable star that has a regular variation in brightness and luminosity due to a periodic expansion and contraction in its outer layers.
Red giant -Red
-Fuse elements other than Hydrogen
Red Supergiant -Red
-Large Surface Area
-Low Surface Temperature
White Dwarfs -Very Small/ Low Surface Area
-Large Surface Temperature
Visual Binary Stars can be distinguished using a telescope
Spectroscopic Binary Analysis if its light spectrum shows 2 different classes of stars- the wavelengths show a periodic splitting in frequency.
Eclipsing binary Analysis of the brightness of its light spectrum shows periodic dips. This is because on star is in the way of the other.
Parsec A unit of distance that is equal to 3.26 light years
Apparent magnitude How bright a star appears from Earth.
Absolute magnitude The apparent magnitude a star would have if it was 10 parsecs away.
Critical density The theoretical density of the universe that would create a flat universe.
Hubble's Law The recessional velocity of a galaxy ? its distance away from Earth.
Audible frequencies 2Hz - 20KHz
(Sound) Intensity Amount of energy that a sound wave brings to a unit area every second.
(Sound) Intensity Level 10 lg (I / I0);
where I0 = 1.0 × 10-12 Wm-2.
Attenuation Coefficient The probability of a single photon being absorbed in 1 m of the material- use defining equation.
Half-value thickness The half-value thickness is that thickness of material which will reduce the intensity of the (transmitted) beam by 50%
Acoustic Impedance The product of of the density of a substance and the speed of sound in that substance.
Exposure The total ionized charge produced in unit mass of air by a particular radiation. Q=mX.
Absorbed Dose The energy absorbed per unit mass of tissue. E=mD.
Quality Factor This allows doses of different types of radiation to be compared for their biological effects.
Dose Equivalent The amount of energy absorbed
Physical Half-Life The time it takes for the activity of a sample
Biological Half-Life The time it takes the body to naturally eject half of an ingested sample of a radioactive isotope.