Modern Physics

Reinventing Gravity  Einstein’s Theory of Special Relativity  Theorizes the space time fabric.  Describes why matter interacts.  The larger the mass the larger the curve in the space time fabric.  Objects that are far away have less interaction  Einstein’s Theory of Special Relativity  Theorizes the space time fabric.  Describes why matter interacts.  The larger the mass the larger the curve in the space time fabric.  Objects that are far away have less interaction

Duality of Light  As seen earlier evidence showed that light can be refracted by gravity.  During an eclipse scientists were able to photograph EM radiation from stars behind the sun.  The gravity of the sun bent the light.  As seen earlier evidence showed that light can be refracted by gravity.  During an eclipse scientists were able to photograph EM radiation from stars behind the sun.  The gravity of the sun bent the light.

Photoelectric Effect (Quantum Theory of Light)  When EM radiation hits an object and the object emits electrons (EX. solar panel)  The electron receives energy from the EM radiation.  They behaved like particles colliding containing a mass and therefore a momentum.  Einstein called these bundles of energy photons.  When EM radiation hits an object and the object emits electrons (EX. solar panel)  The electron receives energy from the EM radiation.  They behaved like particles colliding containing a mass and therefore a momentum.  Einstein called these bundles of energy photons.

So is light a wave or a particle?  Both are correct but also both are incomplete.  Lights dual nature is to this day unexplained in full.  Wave theory - a beam of electrons move as a wave also.  Particle theory - higher intensity should equal higher energy electrons  Actually higher frequency light yields higher energy e’s Animation  E =hf or E=hc/  E is the energy of the photon  h is Planck’s constant (on PRT)  f is the frequency of the light  Both are correct but also both are incomplete.  Lights dual nature is to this day unexplained in full.  Wave theory - a beam of electrons move as a wave also.  Particle theory - higher intensity should equal higher energy electrons  Actually higher frequency light yields higher energy e’s Animation  E =hf or E=hc/  E is the energy of the photon  h is Planck’s constant (on PRT)  f is the frequency of the light

Sample Problem #1  Find the energy of a photon of violet light with a frequency of 7.69x10 14 Hz.  E = hf  E = (6.63x Js)(7.69x10 14 Hz)  E = 5.1x J  Find the energy of a photon of violet light with a frequency of 7.69x10 14 Hz.  E = hf  E = (6.63x Js)(7.69x10 14 Hz)  E = 5.1x J

Sample Problem #2  The wavelength of a certain color of light is 6.1x10 -7 m. What is the energy of the photons of light?  E=hc/  E= ((6.63x Js)(3.00x10 8 m/s))/(6.1x m)  E = 3.26x J  The wavelength of a certain color of light is 6.1x10 -7 m. What is the energy of the photons of light?  E=hc/  E= ((6.63x Js)(3.00x10 8 m/s))/(6.1x m)  E = 3.26x J

Physics and the Atom  What happens when light hits an object but does not impart enough energy to cause the object to emit electrons?  The Bohr model answers this  Electrons with the least amount of energy are in the ground state.  If an electron absorbs energy it can transition to a higher energy level called an excited state.  What happens when light hits an object but does not impart enough energy to cause the object to emit electrons?  The Bohr model answers this  Electrons with the least amount of energy are in the ground state.  If an electron absorbs energy it can transition to a higher energy level called an excited state.

 For an electron to jump energy levels it must absorb the exact amount of energy needed.  The electrons quickly return to ground state and a photon is emitted.  Energy of photon is equal to the energy difference between the excited state and the ground state.  E photon = E i - E f  We will study 2 elements, Mercury and Hydrogen (PRT’s) *******Energy is given in eV, needs to change to J when using Einstein’s equations********  For an electron to jump energy levels it must absorb the exact amount of energy needed.  The electrons quickly return to ground state and a photon is emitted.  Energy of photon is equal to the energy difference between the excited state and the ground state.  E photon = E i - E f  We will study 2 elements, Mercury and Hydrogen (PRT’s) *******Energy is given in eV, needs to change to J when using Einstein’s equations********

Sample Problem  An electron in an excited hydrogen atom drops from the second level to the first energy level. Calculate the energy, and the frequency of the photon emitted.  E photon = E i - E f  E = (-13.6)  E = 10.2eV  (10.2 eV)(1.6x J/eV) = 1.62x J  E=hf  f=E/h  f = 1.62x J/ 6.63x Js  f = 2.4 x10 15 Hz  An electron in an excited hydrogen atom drops from the second level to the first energy level. Calculate the energy, and the frequency of the photon emitted.  E photon = E i - E f  E = (-13.6)  E = 10.2eV  (10.2 eV)(1.6x J/eV) = 1.62x J  E=hf  f=E/h  f = 1.62x J/ 6.63x Js  f = 2.4 x10 15 Hz

Sample #2  Is it possible for a Hydrogen atom to absorb 0.47eV? If so what energy level jump is this associated with?  n=4 -> n=6  -0.38eV - (-.85eV) =.47eV  Is it possible for a Hydrogen atom to absorb 0.47eV? If so what energy level jump is this associated with?  n=4 -> n=6  -0.38eV - (-.85eV) =.47eV

Subatomic Physics  Nucleus  Protons  Positive charge  Mass of 1u or 9.31x10 2 MeV  Neutrons  Neutral charge  Mass of 1u  These are called nucleons  Nucleus  Protons  Positive charge  Mass of 1u or 9.31x10 2 MeV  Neutrons  Neutral charge  Mass of 1u  These are called nucleons

Binding Energy (mass defect)  When comparing the mass of nucleus and the sum of the particles that make it up, the mass of the nucleus is less that the sum of the parts.  Einstein theorized this missing mass was turned into energy used to hold the nucleus together.  Hence E=mc 2  E is energy  m is mass  c is the speed of light  The energy becomes two forces in the atom.  When comparing the mass of nucleus and the sum of the particles that make it up, the mass of the nucleus is less that the sum of the parts.  Einstein theorized this missing mass was turned into energy used to hold the nucleus together.  Hence E=mc 2  E is energy  m is mass  c is the speed of light  The energy becomes two forces in the atom.

Binding Energy Forces  Strong Nuclear Force  An attractive force that hold nucleons together. Or else protons will repel.  Only effective over very short ranges  Weak Nuclear Force  The interaction between protons and electrons.  Appears only during Beta decay as Neutron become protons and emit electrons.  These two plus gravity and electromagnetic forces are the 4 known forces of the universe.  Strong Nuclear Force  An attractive force that hold nucleons together. Or else protons will repel.  Only effective over very short ranges  Weak Nuclear Force  The interaction between protons and electrons.  Appears only during Beta decay as Neutron become protons and emit electrons.  These two plus gravity and electromagnetic forces are the 4 known forces of the universe.

Elementary Particles  Protons, neutrons and electrons were thought to be the smallest particles until  The invention of particle accelerators and particle detectors have since led to the discovery of over 200 new particles.  They do not exist separately for very long.  Particle detectors measure how gas and other materials interact with these new particles.  Protons, neutrons and electrons were thought to be the smallest particles until  The invention of particle accelerators and particle detectors have since led to the discovery of over 200 new particles.  They do not exist separately for very long.  Particle detectors measure how gas and other materials interact with these new particles.

Force Particles  Theoretical physicists have proposed that the forces are an exchange of particles between two objects.  Strong Nuclear Force - gluon particles  Weak Nuclear Force - W + W - Z gauge bosons  Electromagnetic Force - photon  Gravity - graviton  All have been detected except for the graviton  Theoretical physicists have proposed that the forces are an exchange of particles between two objects.  Strong Nuclear Force - gluon particles  Weak Nuclear Force - W + W - Z gauge bosons  Electromagnetic Force - photon  Gravity - graviton  All have been detected except for the graviton

Classifying Matter  Open Reference tables to page 3  All matter is either a hadron or a lepton.  Leptons do not interact via strong nuclear force, hadrons do.  Leptons  6 known - including electrons and neutrinos (no charge, less mass than an electron, result of nuclear reactions on the sun)  Hadrons  Split into Baryons and Mesons both made up of quarks.  Open Reference tables to page 3  All matter is either a hadron or a lepton.  Leptons do not interact via strong nuclear force, hadrons do.  Leptons  6 known - including electrons and neutrinos (no charge, less mass than an electron, result of nuclear reactions on the sun)  Hadrons  Split into Baryons and Mesons both made up of quarks.

Quarks  6 quarks that carry a fractional charge.  Each quark is a different flavor, up, down, strange, charm, top, bottom.  3 quarks combine to make a baryon such as a proton (uud). Composed of 2 up quarks and 1 down.  By charge: +2/3e + +2/3e + -1/3e = +1e  All baryons must be made of quarks whose charge equals a whole number(+ or - )  6 quarks that carry a fractional charge.  Each quark is a different flavor, up, down, strange, charm, top, bottom.  3 quarks combine to make a baryon such as a proton (uud). Composed of 2 up quarks and 1 down.  By charge: +2/3e + +2/3e + -1/3e = +1e  All baryons must be made of quarks whose charge equals a whole number(+ or - )

Anti-particles  For each particle, there is a corresponding antiparticle which has an opposite charge but the same mass.  Ex. Positron or anti-electron has the same mass as an electron but an opposite charge.  These particles only exist for short periods of time. When they interact with their counterpart, they may annihilate releasing photons and gamma rays.  Ex. Cosmic radiation  Anti-particle or anti-matter has only been found in particle accelerators  For each particle, there is a corresponding antiparticle which has an opposite charge but the same mass.  Ex. Positron or anti-electron has the same mass as an electron but an opposite charge.  These particles only exist for short periods of time. When they interact with their counterpart, they may annihilate releasing photons and gamma rays.  Ex. Cosmic radiation  Anti-particle or anti-matter has only been found in particle accelerators

Mesons  Composed of a quark and an anti-quark.  Less massive than baryons.  Always have a charge that is a whole number.  Exist for s.  Composed of a quark and an anti-quark.  Less massive than baryons.  Always have a charge that is a whole number.  Exist for s.

Grand Unified Theory (GUT)  The physics on a large scale does not match the physics on a quantum scale.  Theories such as string theory are trying to tie the two together in order to create a single theory that describes the entire universe.  Problem: string theory requires a minimum of 6 dimensions of which we only know 4. Hypothetically up to 11 dimensions.  The physics on a large scale does not match the physics on a quantum scale.  Theories such as string theory are trying to tie the two together in order to create a single theory that describes the entire universe.  Problem: string theory requires a minimum of 6 dimensions of which we only know 4. Hypothetically up to 11 dimensions.