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Fisika Modern Pertemuan 4-5 Basic Atomic Physics Hadi Nasbey, M.Si <ul><li>Jurusan Fisika </li></ul><ul><li>Fakultas Matem...
Outline <ul><li>Origin of Characteristic X-rays </li></ul><ul><li>The discovery of X-rays by Roentgen </li></ul><ul><li>Ra...
K α 01/02/11 ©  2010 Universitas Negeri Jakarta  |  www.unj.ac.id  | n=4 n=3 n=2 n=1 K γ K β L β L α L γ N=5
<ul><li>electrons were accelerated to high speeds in a discharge tube and allowed to strike the glass of the envelope or a...
<ul><li>Assignment </li></ul><ul><li>Write a short account on the uses of x-ray in radiology </li></ul><ul><li>Hand it out...
-ve electrode +ve electrode 01/02/11 ©  2010 Universitas Negeri Jakarta  |  www.unj.ac.id  |
E=eV X-Ray Ejected electron 01/02/11 ©  2010 Universitas Negeri Jakarta  |  www.unj.ac.id  |
01/02/11 For K transitions For any transitions Continuous spectrum Line spectrum ©  2010 Universitas Negeri Jakarta  |  ww...
01/02/11 ©  2010 Universitas Negeri Jakarta  |  www.unj.ac.id  |
<ul><li>E= e V   =  h f  max , X-rays of maximum energy </li></ul>,   =   K , L, M If, however, the electron loses a cer...
<ul><li>An X-ray tube operates at a potential difference 150 kV. What is the short wavelength limit of the X-radiation emi...
Becquerel   discovered while working with uranium salts that they emitted particles or radiation which could affect photog...
<ul><li> - particles </li></ul><ul><li>He nucleus, +2e,  </li></ul><ul><li> - particles, </li></ul><ul><li>-1e, and +1e ...
01/02/11 ©  2010 Universitas Negeri Jakarta  |  www.unj.ac.id  |
<ul><li>Each nucleus has a fixed probability of decaying per unit time. Nothing affects this probability (e.g.,  temperatu...
01/02/11 Here T 1/2  is the half-life, the time it takes for half the nuclei to decay - i.e. for A to decrease to A/2.  He...
N o -N(t)= N o ( 1- e -  t  )  01/02/11 ©  2010 Universitas Negeri Jakarta  |  www.unj.ac.id  | 14 C  14 N
Ln N(t)= Ln N o  -  t Ln x = 2.3 Log x 01/02/11 ©  2010 Universitas Negeri Jakarta  |  www.unj.ac.id  | Ln N(t)  Ln N o  ...
<ul><li>I (x)  = I 0  e -µx   </li></ul>The main processes by which X- and  γ -rays are absorbed are  photo­electric effec...
+ - Pair production 01/02/11 ©  2010 Universitas Negeri Jakarta  |  www.unj.ac.id  | E=hƒ E”=hƒ” Compton Photoelectric
I (x)  = I 0  e -µx   01/02/11 ©  2010 Universitas Negeri Jakarta  |  www.unj.ac.id  |
Ln I= Ln I o - µx 01/02/11 ©  2010 Universitas Negeri Jakarta  |  www.unj.ac.id  |
<ul><li>The linear absorption coefficient for  K α - and  K β - radiation of silver are 155 cm -1  </li></ul><ul><li>and 6...
5-3 Radiation Units roentgen  (R) •  measures exposure (ionization) of air by X-rays & gamma-rays Quantity of x-rays which...
<ul><li>Estimates biological damage or health risk due to absorption of ionizing radiation </li></ul><ul><li>rem  ( R oeng...
<ul><li>Radiation  QF(approximate) </li></ul><ul><li>_______________________________ </li></ul><ul><li>X or  γ - ray  1 </...
<ul><li>Thus, if a person receives a 0.2-rad dose of  α -particles, the  exposure is measured as (0.2 rad) x (20) = 4 rem...
Terrestrial Sources 5-4 Radiation hazards The average annual dose to the general  population from natural background  and ...
<ul><li>Nuclear plant workers   </li></ul><ul><li>must receive a dosage of no more than  5  rem   per year  ( 40 times the...
Time 5-5 Radiation Protection Distance Shielding All workers are required to wear film badges or pocket ionization chamber...
TERIMA KASIH 01/02/11 ©  2010 Universitas Negeri Jakarta  |  www.unj.ac.id  |
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Fisika Modern (4) basic atomicphysics

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Fisika Modern (4) basic atomicphysics

  1. 1. Fisika Modern Pertemuan 4-5 Basic Atomic Physics Hadi Nasbey, M.Si <ul><li>Jurusan Fisika </li></ul><ul><li>Fakultas Matematika dan Ilmu Pengetahuan Alam </li></ul>01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  2. 2. Outline <ul><li>Origin of Characteristic X-rays </li></ul><ul><li>The discovery of X-rays by Roentgen </li></ul><ul><li>Radioactivity </li></ul><ul><li>Fundamental law of radioactive decay </li></ul><ul><li>The Absorption of γ-Rays and X-Rays </li></ul><ul><li>Radiation Units </li></ul>01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  3. 3. K α 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | n=4 n=3 n=2 n=1 K γ K β L β L α L γ N=5
  4. 4. <ul><li>electrons were accelerated to high speeds in a discharge tube and allowed to strike the glass of the envelope or an anode, some kind of radiation or particle , which he called X-rays , and which could affect a photographic plate, was being given off. </li></ul>01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  5. 5. <ul><li>Assignment </li></ul><ul><li>Write a short account on the uses of x-ray in radiology </li></ul><ul><li>Hand it out before 28/7/2010 </li></ul>01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  6. 6. -ve electrode +ve electrode 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  7. 7. E=eV X-Ray Ejected electron 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  8. 8. 01/02/11 For K transitions For any transitions Continuous spectrum Line spectrum © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  9. 9. 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  10. 10. <ul><li>E= e V = h f max , X-rays of maximum energy </li></ul>,  =  K , L, M If, however, the electron loses a certain amount of energy by collision in the target before producing X-radiation, its energy when it radiates is less than the maximum possible energy,  ›  0 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  11. 11. <ul><li>An X-ray tube operates at a potential difference 150 kV. What is the short wavelength limit of the X-radiation emitted? What energy does one quantum of this radiation carry? </li></ul><ul><li> Solution </li></ul><ul><li>1eV=1.6x10 -19 J </li></ul><ul><li>150 x 10 3 eV x 1.60 x 10 -16 J eV -1 = 2.4 x 10 -14 J. </li></ul>01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  12. 12. Becquerel discovered while working with uranium salts that they emitted particles or radiation which could affect photographic plates. Rutherford and others began an extensive investigation of the phenomenon, the main lines of research being into (a) what sort of particles were being emitted, (b)what sort of laws the emission mechanism obeyed . 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  13. 13. <ul><li> - particles </li></ul><ul><li>He nucleus, +2e, </li></ul><ul><li> - particles, </li></ul><ul><li>-1e, and +1e </li></ul><ul><li> - rays, </li></ul><ul><li>electromagnetic radiation </li></ul>01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  14. 14. 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  15. 15. <ul><li>Each nucleus has a fixed probability of decaying per unit time. Nothing affects this probability (e.g., temperature, pressure, bonding environment, etc.) </li></ul><ul><li>This is equivalent to saying that averaged over a large enough number of atoms the number of decays per unit time is proportional to the number of atoms present. </li></ul><ul><li>Therefore in a closed system: </li></ul><ul><ul><li>N = number of parent nuclei at time t </li></ul></ul><ul><ul><li> = decay constant = probability of decay per unit time (units: s –1 ) </li></ul></ul><ul><li>To get time history of number of parent nuclei, integrate </li></ul><ul><ul><li>N o = initial number of parent nuclei at time t = 0. </li></ul></ul>01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  16. 16. 01/02/11 Here T 1/2 is the half-life, the time it takes for half the nuclei to decay - i.e. for A to decrease to A/2. Here  is called the average lifetime. A=Activity=  N A (t) =½ A o , at t=T 1/2  - Units time -1 (s -1, d -1 , m -1 , y -1 ) © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  17. 17. N o -N(t)= N o ( 1- e -  t ) 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 14 C 14 N
  18. 18. Ln N(t)= Ln N o -  t Ln x = 2.3 Log x 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | Ln N(t) Ln N o Time, t
  19. 19. <ul><li>I (x) = I 0 e -µx </li></ul>The main processes by which X- and γ -rays are absorbed are photo­electric effect Pair production Lead Shield Lead Shield Compton Effect Ln I= Ln I o - µx Detector 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | I 0 I (x ) x
  20. 20. + - Pair production 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | E=hƒ E”=hƒ” Compton Photoelectric
  21. 21. I (x) = I 0 e -µx 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  22. 22. Ln I= Ln I o - µx 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  23. 23. <ul><li>The linear absorption coefficient for K α - and K β - radiation of silver are 155 cm -1 </li></ul><ul><li>and 661 cm -1 when palladium is used as an absorber. What thickness of </li></ul><ul><li>palladium foil reduces the intensity of the K α radiation to one-tenth of its </li></ul><ul><li>incident value? What is then the percentage reduction to the intensity of the K β - radiation? </li></ul><ul><li>Solution </li></ul><ul><li>If the K α - radiation is to be reduced to one-tenth of its incident value, the thickness required is0.0149 m </li></ul><ul><li>For the K β radiation for this thickness of absorber, </li></ul><ul><li>The percentage reduction in the intensity of the K  radiation is 99.995%. </li></ul>01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  24. 24. 5-3 Radiation Units roentgen (R) • measures exposure (ionization) of air by X-rays & gamma-rays Quantity of x-rays which loses 8.34x10 -7 j/g of air rad (radiation absorbed dose) • measures energy deposited in any material by any type of ionizing radiation 1 rad = 0.01 J/kg 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  25. 25. <ul><li>Estimates biological damage or health risk due to absorption of ionizing radiation </li></ul><ul><li>rem ( R oengten E quivalent to M an) </li></ul><ul><li>The biological effect of radiation depends on </li></ul><ul><li>1-the absorbed dose in rads </li></ul><ul><li>2- the QF value of the radiation, </li></ul><ul><li>3- the rad distribution within the tissue, </li></ul><ul><li>4- Certain biological and chemical variables. </li></ul><ul><li>Dose equivalent in rem = (absorbed dose in rad ) x QF </li></ul>01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  26. 26. <ul><li>Radiation QF(approximate) </li></ul><ul><li>_______________________________ </li></ul><ul><li>X or γ - ray 1 </li></ul><ul><li>Electron ( β - particles) 1 </li></ul><ul><li>α - particles 20 </li></ul><ul><li>Protons 10 </li></ul><ul><li>Fast neutrons (~MeV) 10 </li></ul><ul><li>Slow neutrons (~eV) 5 </li></ul><ul><li>_______________________________ </li></ul>01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  27. 27. <ul><li>Thus, if a person receives a 0.2-rad dose of α -particles, the exposure is measured as (0.2 rad) x (20) = 4 rem. </li></ul><ul><li>If the exposure is entirely to X radiation or electrons, the dose equivalent in rem is equal to the dose in rad </li></ul>01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  28. 28. Terrestrial Sources 5-4 Radiation hazards The average annual dose to the general population from natural background and man-made sources is 360 mrem. Cosmic Radiation Internal Sources Other Radon Radon 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  29. 29. <ul><li>Nuclear plant workers </li></ul><ul><li>must receive a dosage of no more than 5 rem per year ( 40 times the natural dosage ) and no more than 3 rem in any period of 13 weeks. </li></ul><ul><li>Anyone working in the vicinity of a radioactive area </li></ul><ul><li>must receive no more than 1.5 rem per year . </li></ul><ul><li>the population as a whole </li></ul><ul><li>must not receive a dosage of more than 0.5 rem per individual per year. </li></ul>01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  30. 30. Time 5-5 Radiation Protection Distance Shielding All workers are required to wear film badges or pocket ionization chambers which, are checked regularly to calculate dosages received 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |
  31. 31. TERIMA KASIH 01/02/11 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |

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