Ch29_part2 - Chapter 29 part 2 PHY213 1 Marie Curie and...

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Unformatted text preview: Chapter 29, part 2 PHY213 1 Marie Curie and Radioactivity s 1867 – 1934 s Discovered new radioactive elements s Shared Nobel Prize (physics in 1903) s Nobel Prize (chemistry in 1911) s Radioactivity is the spontaneous emission of radiation s Experiments suggested that radioactivity was the result of the decay, or disintegration, of unstable nuclei Radioactivity – Types s Three types of radiation can be emitted s Alpha particles ( α ) s The particles are 4 He nuclei s Beta particles ( β + or β- ) s The particles are either electrons or positrons s A positron is the antiparticle of the electron s It is similar to the electron except its charge is +e s Gamma rays ( γ ) s The “rays” are high energy photons Distinguishing Types of Radiation s A radioactive beam is directed into a region with a magnetic field s The gamma particles carry no charge and they are not deflected s The alpha particles are deflected upward s The beta particles are deflected downward s A positron would be deflected upward Penetrating Ability of Particles s Alpha particles s Barely penetrate a piece of paper s Beta particles s Can penetrate a few mm of aluminum s Gamma rays s Can penetrate several cm of lead Chapter 29, part 2 PHY213 2 The Decay Constant s The number of particles that decay in a given time is proportional to the total number of particles in a radioactive sample s ∆N = -λ N ∆t s λ is called the decay constant and determines the rate at which the material will decay s The decay rate or activity , R, of a sample is defined as the number of decays per second N R N t λ ∆ = = ∆ Decay Curve s The decay curve follows the equation, N = N o e- λt s The half-life is also a useful parameter s The half-life is defined as the time it takes for half of any given number...
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This note was uploaded on 08/25/2009 for the course PHY 213 taught by Professor Cao during the Summer '08 term at Kentucky.

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Ch29_part2 - Chapter 29 part 2 PHY213 1 Marie Curie and...

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