Physics Past Paper Facts
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How to use an electronic balance
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Set at zero Place on a stable flat surface
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Refraction definition
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The change in direction of waves at a boundary
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Refractive index =
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Sin i / Sin r
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Using a graph to find the refractive index
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Graph Sin i against Sin r Gradient gives refractive index Graph is a straight line
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Sources of background radiation
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Rocks Radon gas Space Cosmic The sun Medical sources Carbon atoms in living things
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How a sound wave moves through air
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Longitudinal Vibration of air molecules Directions of vibration and propagation are parallel Pressure wave
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Energy transferred =
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Voltage X Current X Time(s)
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Disadvantages of a series circuit
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If one breaks, then none will work Theres no independant controll
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Advantages of a series circuit
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Fewer wires Lower resistance values
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An orbiting object travels faster when its closer to earth
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GPE reduces when you're closer So kinetic energy increases Because total energy is conserved Gravitational field strength increases when closer Mass remains constant So it accelerates
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Difference between X-Ray and visible light
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X-Rays have a shorter wavelength X-Rays have a higher frequency X-Rays have higher energy X-Rays have greater effect on living tissue
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How microwaves work
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Microwaves are electromagnetic waves The waves penetrate into the food This causes the particles to vibrate more The conduction happens through the rest of the food
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Isotopes
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Same protons, different neutrons
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Radioactive atoms
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Unstable nucleus
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Ionisation definition
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Atoms with no charge are turned into ions with charge Happens when nuclear radiation bashes into atoms
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Geiger-Muller detector
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Detects ionising radiation
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Alpha particles
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2 protons and 2 neutrons
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Alpha particles charge
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+2
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Alpha particles ionisation
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Strong ionisation
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Beta particles
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Fast moving electron A neutron has turned into a proton and an electron
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Beta particles charge
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-1
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Beta particles ionisation
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Moderately ionising
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Gamma radiation
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E.M wave No mass
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Gamma ionisation
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Weekly ionising
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Blocks alpha particles
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Paper, skin
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Blocks beta particles
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Thin metal
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Blocks gamma rays
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Thick lead, very thick concrete
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Alpha particles effect
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Atomic number: -2 Mass number: -4
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Beta particles effect
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Atomic number +1 Mass number: X
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Gamma rays effect
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Atomic number: X Mass number: X
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Half life definition
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The time is takes for half of the radioactive atoms to decay
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When recording radioactivity
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Subtract background radiation from your reading
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Use of Beta or Gamma
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Medical tracers
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Use of Gamma radiation
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Industrial tracers e.g. pipe
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Radioactive dating of rocks
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Find half life Compare proportions of uranium and lead isotopes Compare proportions of C 14 and C 12
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When radiation enters the body
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Collides with molecules in cells Ionisation Damages or destroys cells OR Mutates cells causing cancer
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Disposing of radioactive waste
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Buried deep underground
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Handling radioactive materials
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Hold with tongs Pointed away from body Store in sealed lead box
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Nuclear fission definition
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Splitting up an atom which releases energy Controlled chain reaction
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Atoms used for nuclear fission
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Uranium and plutonium
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Nuclear fission
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A slow moving neutron gets absorbed by a uranium nucleus The nucleus splits and spits out neutrons 2 radioactive daughter nuclei are made
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Nuclear reactor
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Moderator slows neutrons so they can collide with atoms Control rods limit the rate of fission by absorbing excess neutrons
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Half-life definition
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The time for half the nuclei in the radioactive sample to decay
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Smoke alarm type of radiation
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Alpha
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Nuclear radiation used to treat cancer
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Beta or Gamma
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Most penetrating radiation
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Gamma
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Nuclear radiation used to steralise surgical instruments
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Gamma
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Most strongly ionising radiation
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Alpha
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Nucleus charge
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Positive
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Why radioactivity experiments are done in a vacuum
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To avoid ionisation To avoid colliding with air particles To provide sufficient distance of movement
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The force that causes alpha particles to deflect
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Electrostatic force Like charges repel
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Frequency =
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Wave speed / wave length
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Magnetic field line definition
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Line that shows direction of the magnetic force
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Gravitational potential energy is affected by
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Centre of gravity
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Frequency =
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1 / time for one wave to pass
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Frequency definition
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Number of waves in a second (Hz)
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Wave speed =
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Frequency X Wavelength
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Longitudinal waves
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Vibrations in the same direction as the wave's direction
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Transverse waves
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Vibrations are perpendicular to the wave's direction
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Diffraction
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When waves bend round edges and through gaps causing the waves to spread out
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Affects the amount of diffraction
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Size of gap Wavelength of wave
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Electromagnetic spectrum order
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Radio waves Microwaves Infrared Visible light Ultraviolet X-rays Gamma rays
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Use of radio waves
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Communication
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Use of microwaves
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Satellite communication
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Use of infrared
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Heating Monitering temperature
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Use of visible light
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Light signals can travel through optical fibres (communication) Photography
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Use of ultraviolet
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Fluorescent lamps
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Use of X-rays
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X rays in hospitals
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Use of gamma radiation
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Sterilising medical equipment Sterilising food
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What all EM waves have in common
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Speed
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EM wave which causes sunburn and snow blindness
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Ultraviolet
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Total internal reflection
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When a light ray is reflected inside a glass block
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Straight line one a graph shows
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Linear relationship / constant rate
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Relationship between light intensity and LDR resistance
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Bright light means low resistance Inverse relationship Non linear relationship
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Why voltage is induced when shaking a magnet torch
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Wire cuts magnetic field
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LED is better than a filament lamp
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Less energy required / less waste heat energy Useful output is closer to total energy input
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Kinetic energy =
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1?2 x mass x velocity(2)
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Why terminal velocity occurs
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Forces are balanced F = m a No acceleration
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Opposing forces on a travelling car
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Air resistance Friction
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Calculating distance from a graph
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1/2 X velocity X time
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Digital signal
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Only 2 values
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Primary voltage X Primary current =
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Secondary voltage X Secondary current
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How you know the reflection is a vertical image
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Rays do not actually meet at the image
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Conditions needed for total internal reflection
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Angle of incidence ; critical angle Must be more 'optically dense to less optically dense' change
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Optical fibres advantages
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Less prone to noise Less prone to heating Send more information per second More data per second
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Role of moderator in a nuclear fission plant
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Slow neutrons
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Direct current
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Current moving in a single direction
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Why radio waves are suitable for communication
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Travel at the speed of light Can code information
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Danger of microwaves to people
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Heating
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Danger of ultraviolet to people
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Skin cancer Sunburn
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How a loudspeaker works
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Current in coil Changing current / alternating current Produces magnetic field Constantly changing field which interacts with field of permanent magnet Force on coil / coil moves Vibration in coil / cone / air makes longitudinal wave
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Using a graph to find the height
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Area underneath the graph
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Gravitational field strength is stronger on earth
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Moon has less mass
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Something hits the ground before the other
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One is lighter so reaches terminal velocity sooner because smaller force is needed Average velocity is smaller
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Efficiency will be higher than expected
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Calculation of useful energy doesn't allow for energy lost
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When temperature hasn't started rising yet
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Energy to transferring between heater and thermometer
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When temperature is rising
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Heat transfers through block by conduction Input energy greater than output energy
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When temperature rise begins to slow down
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Energy lost to surroundings by radiation
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Total internal reflection definition
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All of light is reflected inside the material
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Uses of total internal reflection
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Prism in camera Optical fibres for communication Optical fibres for decorative lamps
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Critical angle equation
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Sin C = 1 / refractive index
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MHz to Hz
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X1000000 (add 6 0s)
