Physics Unit 1

Physics Unit 1

1. Section 1: Particles and Radiation

   • Atomic Structure
     • Protons have a mass of 1.67 x 10-27
     • Protons have a charge of +1.6 x 10-19
     • Neutrons have a charge of 0
     • Neutrons have a mass of 1.67 x 10-27
     • Electron has a mass of 9.11 x 10-31
     • Electron has a charge of -1.6 x 10-19
     • Specific Charge = charge/mass
     • Isotopes are atoms with the same number of protons and different number of neurtons
   • Stable and Unstable Nuclei
     • Strong nuclear force
       • Holds the nucleus together
       • <0.5fm: High Repulsive
       • 0.5fm - 3fm: High Attraction, High Repulsive Electromagnetic force
       • >3fm: Low Repulsive Electromagnetic force, Low Attractive
     • Alpha Decay
       • 4 2 helium nuclei
       • Nuclion number -4
       • Proton Number -2
     • Beta Decay
       • Stray electron
       • Anti-neutrino
       • Nucion Number stays the same
       • Proton number +1
   • AntiParticles and Photons
     • Photons
       • EM (Electromagnetic) waves can only exist in wave-packets "Photons"
       • E = hf
       • E = hc/wavelength
       • h = Plank's constant (6.63 x 10-34)
     • Antiparticles
       • Example: electron and positron
       • Same mass
       • Opposite charge
   • Pair Production
     • When energy is converted into mass
     • Only can happen when there is enough enegy to produce the mass needed
     • Makes the same amounts of particles and antiparticles
   • Annihilation
     • When a particle meets its antiparticle
     • All of the mass become Gamma Photon energy
   • Classification of particles
     • Hadrons
       • Baryons
         • Nucleons p,n, sigma, others
       • Mesons
         • Pions, Kaons, others
     • Leptons
       • Electrons
   • Quarks and antiquarks
     • Protons: uud
     • Nutrons: udd
     • Quark Confinement
       • A Proton
         • Energy is supplied to remove u quark
           • When enough energy is suppied the u quark pari produces and the u quark stays in the proton
   • Conservation of properties
     • Charge
       • Any particle reaction
     • Baryon and lepton numbers
       • Any particle reaction
     • Strangness
       • Only strong interactions
   • Feynaman Diagrams
     • Beta - Minus
     • Beta - Plus
     • Electron Capture
     • Electron - proton collisions
     • Electromagnetic Repulsion

2. Section 2: Electromagnetic Radiation and Quantum Phenomena

   • The Photoelectric effect
     • If enough energy is absorbed by a metal the free electrons will be emitted
     • 4 Conclusions
       • No electrons emitted underthreshold frequency
       • The maximum kinetic energy increases with the frequency of the radiation
       • The maximum kinetic energy is unaffected by the intensity of the radiation
       • The number of electrons emitted per second is proportional to the intensity of the radiation
     • E = hf = hc/wavelength
       • E= energy in 1 wave-packet
       • h= planks constant = 6.63x10-34
       • c = speed of light 3x108
     • Work Function: the energy needed to break the bonds holding the electron
     • Threshold frequency = workfunction/h
     • Maximum Kinetic energy
       • hf = workfunction + Ek
       • hf = work function + 1/2mv^2
   • Energy levels in atoms
     • 1 eV = 1.6x10-19 J
     • electrons can ony exist in defined levels
       • n = 1 is ground state
       • Electrons can only move states by emitting a photon
         • The energy of these photons can only take a certain value
     • electrons can move up levels if they absorb a photon
       • movment of an electron to a higher level is called excitation
         • ^E = E1 - E2 = hf = hc/wavelength
           • the transmission of an electron from n1 to n2
     • ionisation energy is the energy needed to remove an electron fromground state
     • Line emission spectra
       • split the light from a fluoresent tube
         • get different colours on a black background
           • shows that electrons exsist in discrete energy levels
     • Line absorbtion spectra
       • split white light you see all the colours
         • all of the electrons are on ground level
   • Wave-particle duality
     • Light a wave or a particle
       • Diffraction
         • if it was a particle it wouldnt diffract
       • photoelectric effect
         • photons are light with particle properties
       • its both known as the wave-particle duality
     • de broglie wavelength = h/mv
     • Electron diffraction
       • shows electrons have wave properties
       • when the velocity of the electrons is greater the wavelength is smaller
     • Electron microscopes
       • the greater the diffraction the more blury the image is
       • smaller wavelength less blur
       • electrons need to be as fast as possible

3. Section 3: Current Electricity

   • Current and potential difference
     • Current
       • Rate of flow of charge
     • P.D
       • the work done to move a unit of charge
     • Q = IT
       • V = W/Q
         • 1 V = 1 JC^-1
   • Resistance
     • how hard it is for current to flow through a component
       • R = V/I
     • Ohmic conductors
       • Current is directly proportional to potential difference if the temperature is constant
   • I-V characteristics
     • Filament lamps
       • when you swith it on and its cold = less resistnce = more current so could blow
         • goes from cold to hot very quickly so could blow
     • finding I-V characteristics
       • Use a variable resistor to to increase or decrease the resistance in equal stepd
         • for each resistance take a reading from the ammeter and voltmeter
           • revserse the flow by switching the wires on the power pack to get negative readings
     • Semiconductors
       • Thermistors
         • as temperature goes up then resistnace goes up
       • Diodes
         • only allows current to flow in one direction
       • LDR
         • as light increases so does resistence
   • Resistivity and superconductors
     • Resistivity
       • resistance of in 1m of wire with 1m^2 cross sectional area
         • p = RA/L
     • Superconductors
       • if you cool some metals under the "transition temperature" then resistance disappears compeletly
         • Uses
           • power calbes
           • strong electromagnets
           • really fast circiuts
   • Power and electrical energy
     • Power
       • P = E/t
         • P = VI
           • P = V^2/I
             • P = I^2R
     • Energy
       • E = VIt
         • E = V^2/R t
           • E = I^2Rt
   • E.M.F and Internal resistance
     • Internal resistnce causes loss of energy inside the battery
       • EMF: the amount of electrical energy the battery produces and transfers to each coulmb of charge
         • emf = E/Q
           • emf = I(R+r)
         • To get internal resistance from a graph make the equation V = -rI +emf draw a graph and -r is the graditet and emf is the y-intercept
   • Conservation of charge in circuits
     • Parallel
       • emf = V1+ V1 + V1
         • I = I1+ I2 + I3
           • 1/R = 1/R1+ 1/R2
     • Series
       • emf = V1+V2+ v3
         • I1= I2 = I3
           • R = R1 + R2 + R3
   • The potential divider
     • Vout = (R2/R1+R2)Vs
   • Alternating Current
     • f = 1/t
     • RMS (Root Mean Square)
       • Vrms = V0/square root of 2
       • Irms = I0/square root of 2
       • Power = Irms x Vrms
         • Resistance = Vrms/Irms = V0/I0
     • I0 = peak current

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