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PHY 112: Physics II

Chapter 30: Nuclear Physics and Radioactivity

Reading Assignment: Giancoli (5th ed) - pages 916 - 937

Objectives:

Be knowledgeable about and capable of working problems in the following areas:

  • Structure and Properties of the Nucleus
  • Binding Energy and Nuclear Forces
  • Radioactivity
  • Alpha Decay
  • Beta Decay
  • Gamma Decay
  • Coservation of Nucleon Number and Other Conservation Laws
  • Half-life and Rate of Decay
  • Calculations Involving decay Rates and Half-life
  • Decay Series
  • Radioactive Dating
  • Stability and Tunneling
  • Detection of Radiation

    key terms and phrasesnucleus of an atom contains protons and neutrons. These particles are called nucleons.

    1 unified atomic mass unit (u) = 1.660 x lO^-27 kg.

    atomic number is the number of protons contained in the nucleus.

    atomic mass number is the total number of protons and neutrons in the nucleus.

    isotopes are atoms which have the same number of protons but different number of neutrons in the nucleus.

    binding energy is the energy required to break apart a nucleus into its constituent protons and neutrons.

    strong nuclear force refers to attractive force which holds the nucleus together. The strong nuclear force acts between all nucleons, protons and neutrons alike. This force is much greater than the force of electrostatic repulsion which exists between the protons. The strong nuclear force is a short-range force. It acts between nucleons if they are less than lO^-15 m apart, but is essentially zero if the separation ditance is greater than 10^-15 m.

    weak nuclear force is much weaker than the strong nuclear force and appears in a type of radioactive decay called beta decay.

    radioactive decay results from the instability of certain nuclei. There are three different radiations produced by radioactive decay: ,b>alpha, beta, and gamma,/b>.

    parent nucleus refers to the nucleus before radioactive decay.

    daughter nucleus refers to the nucleus after radioactive decay.

    alpha decay occurs when a helium nucleus is spontaneously ernitted from the nucleus. An alpha particle consists of two protons and two neutrons but no electrons.

    disintegration energy (Q) is the total energy released during alpha decay.

    beta decay occurs when an electron (e-) and an antineutrino (v-bar) are spontaneously emitted from the nucleus. Beta decay (beta -) is observed in nuclei which have a high ratio of neutrons to protons.

    electron capture occurs when the nucleus absorbs one of the inner orbital electrons in the atom to form a neutron.

    transmutation is the changing of one element into a new element. Transmutation is the result of alpha or beta decay.

    gamma decay occurs when a nucleus in an excited state drops to a lower energy state. In the process a photon called a gamma ray (gamma) is emitted.

    law of conservation of nucleon number states that the total number of nucleons before decay equals the total number of nucleons after decay.

    half-life of an isotope is the time required for half of the radioactive nuclei present in the sample to decay.

    radioactive decay series is a series of successive decays which starts with one parent isotope and proceeds through a number of daughter isotopes. The series ends when a stable, nonradioactive isotope is produced.

    radioactive dating refers to a method of estimating the age of an object based on the object's half-life and the amount of the isotope present in the sample being analyzed.

    Problem Assignment:

    The following problems should be worked to assist you in meeting the Chapter Objectives.
    Problem 3 Page 940
    Problem 11 Page 940
    Problem 19 Page 940
    Problem 37 Page 941
    Problem 39 Page 941

    Tutorial Links

    Physics Tutorial from Prentice Hall

    Peter Jeschofnig, Ph.D., Professor of Science, Colorado Mountain College


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    This page was created by Peter Jeschofnig and was last updated: 1/17/2002