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5.3 Nuclear physics G485 Fields, Particles, Frontiers of Physics 5.3 Nuclear physics G485 Fields, Particles, Frontiers of Physics Mr Powell 2012 Index.

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Presentation on theme: "5.3 Nuclear physics G485 Fields, Particles, Frontiers of Physics 5.3 Nuclear physics G485 Fields, Particles, Frontiers of Physics Mr Powell 2012 Index."— Presentation transcript:

1 5.3 Nuclear physics G485 Fields, Particles, Frontiers of Physics 5.3 Nuclear physics G485 Fields, Particles, Frontiers of Physics Mr Powell 2012 Index The Nuclear Atom The Nuclear Atom Fundamental Particles Fundamental Particles Radioactivity Radioactivity Fission and Fusion Fission and Fusion

2 Mr Powell Nuclear Physics Assessable learning outcomes.. (a) describe qualitatively the alpha-particle scattering experiment and the evidence this provides for the existence, charge and small size of the nucleus. (b) describe the basic atomic structure of the atom and the relative sizes of the atom and the nucleus; (c) select and use Coulombs law to determine the force of repulsion, and Newtons law of gravitation to determine the force of attraction, between two protons at nuclear separations and hence the need for a short-range, attractive force between nucleons (d) describe how the strong nuclear force between nucleons is attractive and very short- ranged; (e) estimate the density of nuclear matter; (f) define proton and nucleon number; (g) state and use the notation.... for the representation of nuclides; (h) define and use the term isotopes; (i) use nuclear decay equations to represent simple nuclear reactions; (j) state the quantities conserved in a nuclear decay. Assessable learning outcomes.. (a) describe qualitatively the alpha-particle scattering experiment and the evidence this provides for the existence, charge and small size of the nucleus. (b) describe the basic atomic structure of the atom and the relative sizes of the atom and the nucleus; (c) select and use Coulombs law to determine the force of repulsion, and Newtons law of gravitation to determine the force of attraction, between two protons at nuclear separations and hence the need for a short-range, attractive force between nucleons (d) describe how the strong nuclear force between nucleons is attractive and very short- ranged; (e) estimate the density of nuclear matter; (f) define proton and nucleon number; (g) state and use the notation.... for the representation of nuclides; (h) define and use the term isotopes; (i) use nuclear decay equations to represent simple nuclear reactions; (j) state the quantities conserved in a nuclear decay.

3 Mr Powell 2014 Alpha Decay.... Alpha particles tracks

4 Mr Powell 2014 (a) describe qualitatively the alpha-particle scattering experiment and the evidence this provides for the existence, charge and small size of the nucleus.

5 Mr Powell 2014 Probing the Nucleus – Rutherford Scattering By firing alpha particles at a heavy gold nucleus Rutherford could easily see that atoms were mostly space with a large positive nucleus in the centre.

6 Mr Powell 2014

7 Scattering Formulae (extension) There are complex formulae that we can use to work out the distance of closest approach. You will not have to learn these but should appreciate some of the maths involved. At the very least the idea of the forces involved

8 Mr Powell 2014 Distance of Closest Approach (extension)

9 Mr Powell 2014 Distance of Closest Approach (extension)

10 Mr Powell 2014

11 Summary Question... For an alpha particle with an initial KE of 6MeV fired at a gold nucleus find the distance of closest approach of the alpha and the nucleus...

12 Mr Powell 2014 Small Nucleus.... Nucleons....

13 Mr Powell 2014 Estimate Nuclear Diameter with Electron Diffraction

14 Mr Powell 2014 Quick Question

15 Mr Powell 2014 (b) describe the basic atomic structure of the atom and the relative sizes of the atom and the nucleus;

16 Mr Powell 2014 (c) select and use Coulombs law to determine the force of repulsion, and Newtons law of gravitation to determine the force of attraction, between two protons at nuclear separations and hence the need for a short-range, attractive force between nucleons

17 Mr Powell 2014 (d) describe how the strong nuclear force between nucleons is attractive and very short-ranged;

18 Mr Powell 2014 Where does it come from? The strong force actually acts between quarks which are found inside nucleons. It's the strong force that causes nucleons to attract. The carrier of this force is the gluon. The force ensures that the protons and neutrons in the nucleus of the atom stay together without flying apart. The nucleus of the atom is formed in this way. This force is so strong that it almost causes the protons and neutrons within the nucleus to bind to each other. This is why the minute particles that possess this force are called "gluon" meaning "glue" in Latin.

19 Mr Powell Equilibrium separation Separation/ fm attraction repulsive Force (no units) Interactions combined.. The overall graph is a combination of electrostatic repulsion (charged quarks) and the strong force (quarks) Typical equilibrium separation Separation/ fm Electric force dominates at larger separations strong nuclear force dominates at smaller separations attraction repulsive Force (no units) u u u u d d d d u u d d Separation/ fm Repulsive Force (N)

20 Mr Powell 2014 Main properties of the strong nuclear force are: 1.At typical nucleon separation (1.3 x m) it is a very strong attractive force (10 4 N). 2.At much smaller separations between nucleons the force is very powerfully repulsive. 3.Beyond about 1.3 x m separation, the force quickly dies off to zero. 4.Thus, the strong nuclear force is a very short-range force. 5.The much smaller Coulomb force between protons has a much larger range and becomes the only significant force between protons when their separation exceeds about 2.5 x m. 6.The strong nuclear force is not connected with charge. Proton-proton, proton- neutron and neutron-neutron forces are the same. (The force between protons, however, must always be modified by the Coulomb repulsion between them.)

21 Mr Powell 2014 Fundamental Forces

22 Mr Powell 2014 ElementAA 1/3 R in fm Carbon Oxygen Silicon Calcium Vanadium Strontium Indium Atomic Radius.... Various types of scattering experiments suggest that nuclei are roughly spherical and appear to have essentially the same density. The data are summarized in the expression called the Fermi model; r 0 = 1.2 x m = 1.2fm r = atomic radius A = mass number (nucleons) Can you plot a graph and show that this formulae is correct and the constant is 1.2fm FACT The diameter of the nucleus is in the range of 1.6fm (1.6 × m) (for a proton in light hydrogen) to about 15 fm (for the heaviest atoms, such as uranium).

23 Mr Powell 2014 Finding R 0

24 Mr Powell 2014 (e) estimate the density of nuclear matter;

25 Mr Powell 2014 Summary & Question 1.Calculate the radius of an oxygen nucleus which has 16 nucleons.. r=r 0 A 1/3 = 1.4 x x (16) 1/3 r=3.5 x m (3.5fm)

26 Mr Powell 2014 Nuclear Density – is massive!

27 Mr Powell 2014 (f) define proton and nucleon number & (g) state and use the notation.... for the representation of nuclides;

28 Mr Powell 2014 (h) define and use the term isotopes;

29 Mr Powell 2014 (i) use nuclear decay equations to represent simple nuclear reactions;

30 Mr Powell 2014 (i) use nuclear decay equations to represent simple nuclear reactions;

31 Mr Powell 2014 (j) state the quantities conserved in a nuclear decay.

32 5.3.1 The Nuclear Atom Covered in my lesson Revised/ Made my own notes or reviewed at home Attempted Exam or Revision Questions (a) describe qualitatively the alpha-particle scattering experiment and the evidence this provides for the existence, charge and small size of the nucleus (b) describe the basic atomic structure of the atom and the relative sizes of the atom and the nucleus; (c) select and use Coulombs law to determine the force of repulsion, and Newtons law of gravitation to determine the force of attraction, between two protons at nuclear separations and hence the need for a short-range, attractive force between nucleons (d) describe how the strong nuclear force between nucleons is attractive and very short-ranged; (e) estimate the density of nuclear matter; (f) define proton and nucleon number; (g) state and use the notation A,Z,X for the representation of nuclides; (h) define and use the term isotopes; (i) use nuclear decay equations to represent simple nuclear reactions; (j) state the quantities conserved in a nuclear decay. Next Steps for me? / (what do I need to ask for help on)

33 Mr Powell 2014 Q2 June The table shows data for some nuclei. 1 eV = 1.6 × J & speed of electromagnetic radiation = 3.0 × 10 8 ms -1 (a) (i) Show that these data support the rule that where R 0 is a constant; R = R 0 A (1/3) (ii) The mass of a nucleon is about 1.7 × kg. Calculate the density of nuclear matter. (6 marks) (b) (i) Explain what is meant by the binding energy of a nucleus. (ii) Show that the total binding energy of a sodium-23 nucleus is about 3 × J. (iii) Calculate the mass-equivalent of this binding energy. (5 marks)

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