1. ConcepTest 27.1Photons 400 nm500 nm600 nm700 nm Which has more energy, a photon of: 1) red light 2) yellow light 3) green light 4) blue light 5) all have the same energy

2. highest frequencymost energy c = f higher frequencylower wavelength blue The photon with the highest frequency has the most energy because E = hf = hc/ (recall that c = f ). So a higher frequency corresponds to a lower wavelength. The highest energy of the above choices is blue. ConcepTest 27.1Photons 400 nm500 nm600 nm700 nm Which has more energy, a photon of: 1) red light 2) yellow light 3) green light 4) blue light 5) all have the same energy E = h f

3. ConcepTest 27.2aPhotoelectric Effect I If the cutoff frequency for light in the photoelectric effect for metal B is greater than that of metal A. Which metal has a greater work function? 1) metal A 2) metal B 3) same for both W 0 4) W 0 must be zero for one of the metals f KE f0f0

4. greatercutoff frequencyhigher energy work function is greater A greater cutoff frequency means a higher energy is needed to knock out the electron. But this implies that the work function is greater, since the work function is defined as the minimum amount of energy needed to eject an electron. ConcepTest 27.2aPhotoelectric Effect I If the cutoff frequency for light in the photoelectric effect for metal B is greater than that of metal A. Which metal has a greater work function? 1) metal A 2) metal B 3) same for both W 0 4) W 0 must be zero for one of the metals f KE f0f0 Follow-up: What would you expect to happen to the work function of a metal if the metal was heated up? of a metal if the metal was heated up?

5. A metal surface with a work function of W 0 = hc/550 nm is struck with blue light and electrons are released. If the blue light is replaced by red light of the same intensity, what is the result? A metal surface with a work function of W 0 = hc/550 nm is struck with blue light and electrons are released. If the blue light is replaced by red light of the same intensity, what is the result? 1) emitted electrons are more energetic 2) emitted electrons are less energetic 3) more electrons are emitted in a given time interval 4) fewer electrons are emitted in a given time interval 5) no electrons are emitted ConcepTest 27.2bPhotoelectric Effect II

6. Red light700 nm 550 nmyellow light maximum wavelength no electrons are knocked out Red light has a wavelength of about 700 nm. The cutoff wavelength is 550 nm (yellow light), which is the maximum wavelength to knock out electrons. Thus, no electrons are knocked out. A metal surface with a work function of W 0 = hc/550 nm is struck with blue light and electrons are released. If the blue light is replaced by red light of the same intensity, what is the result? A metal surface with a work function of W 0 = hc/550 nm is struck with blue light and electrons are released. If the blue light is replaced by red light of the same intensity, what is the result? 400 nm500 nm600 nm700 nm energy low high E = hc / E = hc / 1) emitted electrons are more energetic 2) emitted electrons are less energetic 3) more electrons are emitted in a given time interval 4) fewer electrons are emitted in a given time interval 5) no electrons are emitted ConcepTest 27.2bPhotoelectric Effect II

7. ConcepTest 27.2cPhotoelectric Effect III A metal surface is struck with light of = 400 nm, releasing a of electrons. If the 400 nm light is replaced by = 300 nm light of the same intensity, what is the result? A metal surface is struck with light of = 400 nm, releasing a stream of electrons. If the 400 nm light is replaced by = 300 nm light of the same intensity, what is the result? 1) more electrons are emitted in a given time interval 2) fewer electrons are emitted in a given time interval 3) emitted electrons are more energetic 4) emitted electrons are less energetic 5) none of the above

8. reducedwavelengthhigherfrequency higher energy more energetic A reduced wavelength means a higher frequency, which in turn means a higher energy. So the emitted electrons will be more energetic, since they are now being hit with higher energy photons. ConcepTest 27.2cPhotoelectric Effect III A metal surface is struck with light of = 400 nm, releasing a of electrons. If the 400 nm light is replaced by = 300 nm light of the same intensity, what is the result? A metal surface is struck with light of = 400 nm, releasing a stream of electrons. If the 400 nm light is replaced by = 300 nm light of the same intensity, what is the result? 1) more electrons are emitted in a given time interval 2) fewer electrons are emitted in a given time interval 3) emitted electrons are more energetic 4) emitted electrons are less energetic 5) none of the above c = f  E = h f Remember that c = f  and that E = h f

9. A metal surface is struck with light of = 400 nm, releasing a stream of electrons. If the light intensity is increased (without changing ), what is the result? A metal surface is struck with light of = 400 nm, releasing a stream of electrons. If the light intensity is increased (without changing ), what is the result? 1) more electrons are emitted in a given time interval 2) fewer electrons are emitted in a given time interval 3) emitted electrons are more energetic 4) emitted electrons are less energetic 5) none of the above ConcepTest 27.2dPhotoelectric Effect IV

10. A metal surface is struck with light of = 400 nm, releasing a stream of electrons. If the light intensity is increased (without changing ), what is the result? A metal surface is struck with light of = 400 nm, releasing a stream of electrons. If the light intensity is increased (without changing ), what is the result? 1) more electrons are emitted in a given time interval 2) fewer electrons are emitted in a given time interval 3) emitted electrons are more energetic 4) emitted electrons are less energetic 5) none of the above higher intensitymore photons more electrons. A higher intensity means a more photons, which in turn means more electrons. On average, each photon knocks out one electron. ConcepTest 27.2dPhotoelectric Effect IV

11. ConcepTest 27.4Ionization ConcepTest 27.4 Ionization How much energy does it take to ionize a hydrogen atom in its ground state? 1) 0 eV 2) 13.6 eV 3) 41.2 eV 4) 54.4 eV 5) 108.8 eV

12. The energy of the ground state is the energy that binds the electron to the nucleus. Thus, an amount equal to this binding energy must be supplied in order to kick the electron out of the atom. ConcepTest 27.4 Ionization How much energy does it take to ionize a hydrogen atom in its ground state? 1) 0 eV 2) 13.6 eV 3) 41.2 eV 4) 54.4 eV 5) 108.8 eV Follow-up: How much energy does it take to change a He + ion into a He ++ ion? Keep in mind that Z = 2 for helium.

13. ConcepTest 27.5aAtomic Transitions I n = 1 n = 2 n = 3 n = 5 n = 4 1) 2  5 2) 5  3 3) 8  5 4) 4  7 5) 15  7 For the possible transitions shown, for which transition will the electron gain the most energy?

14. ConcepTest 27.5aAtomic Transitions I n = 1 n = 2 n = 3 n = 5 n = 4 1) 2  5 2) 5  3 3) 8  5 4) 4  7 5) 15  7 higher higher n The electron must go to a higher orbit (higher n) in order for the electron to gain energy. Because of the 1/n 2 dependence: E 2 – E 5 > E 4 – E 7 For the possible transitions shown, for which transition will the electron gain the most energy? Follow-up: Which transition will emit the shortest wavelength photon?

15. n = 1 n = 2 n = 3 n = 5 n = 4 n =  n = 6 The Balmer series for hydrogen can be observed in the visible part of the spectrum. Which transition leads to the reddest line in the spectrum? 1) 3  2 2) 4  2 3) 5  2 4) 6  2 5)   2 ConcepTest 27.5bAtomic Transitions II

16. 3  2 lowest energylowest frequency longest wavelength reddest The transition 3  2 has the lowest energy and thus the lowest frequency photon, which corresponds to the longest wavelength (and therefore the “reddest”) line in the spectrum. n = 1 n = 2 n = 3 n = 5 n = 4 n =  n = 6 The Balmer series for hydrogen can be observed in the visible part of the spectrum. Which transition leads to the reddest line in the spectrum? 1) 3  2 2) 4  2 3) 5  2 4) 6  2 5)   2 ConcepTest 27.5bAtomic Transitions II Follow-up: Follow-up: Which transition leads to the shortest wavelength photon?

17. ConcepTest 27.6Balmer Series When a broad spectrum of light passes through hydrogen gas at room temperature, absorption lines are observed that correspond only to the Balmer (n f = 2) series. Why aren’t other series observed? 1) they’re there, but they’re invisible 2) only the Balmer series can be excited at room temperature 3) the other series have been ionized 4) all the photons have been used up

18. ConcepTest 27.6 Balmer Series When a broad spectrum of light passes through hydrogen gas at room temperature, absorption lines are observed that correspond only to the Balmer (n f = 2) series. Why aren’t other series observed? 1) they’re there, but they’re invisible 2) only the Balmer series can be excited at room temperature 3) the other series have been ionized 4) all the photons have been used up wavelengths in the visible part The Balmer series is the only one that involves wavelengths in the visible part of the spectrum! Follow-up: Follow-up: From the diagram at right, where in the EM spectrum is the Lyman series located?

19. ConcepTest 27.7aEnergy Levels I n = 1 n = 2 n = 3 n = 5 n = 4 Suppose there is an atom that contains exactly five energy levels. How many different transitions are possible? (Count only one direction!) 1) 4 2) 5 3) 10 4) 20 5) many more than 20

20. ConcepTest 27.7aEnergy Levels I n = 1 n = 2 n = 3 n = 5 n = 4 upward Just count them! Transitions upward: n = 1  n = ? 4 transitions n = 2  n = ? 3 transitions n = 3  n = ? 2 transitions n = 4  n = ? 1 transition This gives a total of 10 possible ones This gives a total of 10 possible ones. Suppose there is an atom that contains exactly five energy levels. How many different transitions are possible? (Count only one direction!) 1) 4 2) 5 3) 10 4) 20 5) many more than 20

21. (1)(2)(3)(4) The emission spectrum for the atoms of a gas is shown. Which of the energy level diagrams below corresponds to this spectrum? ConcepTest 27.7bEnergy Levels II

22. (1)(2)(3)(4) transition 6 transitions4 levels The 2 transitions between the closely spaced levels have less energy, while the other 4 have larger energies Each line in the spectrum corresponds to a transition between energy levels! Since there are 6 transitions shown, there must be 4 levels. The 2 transitions between the closely spaced levels have less energy, while the other 4 have larger energies. The emission spectrum for the atoms of a gas is shown. Which of the energy level diagrams below corresponds to this spectrum? ConcepTest 27.7bEnergy Levels II

23. ConcepTest 30.1 The Nucleus There are 82 protons in a lead nucleus. Why doesn’t the lead nucleus burst apart? 1) Coulomb repulsive force doesn’t act inside the nucleus 2) gravity overpowers the Coulomb repulsive force inside the nucleus 3) the negatively charged neutrons balance the positively charged protons 4) protons lose their positive chargeinside the nucleus 5) none of the above

24. nuclear force The Coulomb repulsive force is overcome by the even stronger nuclear force! ConcepTest 30.1 The Nucleus There are 82 protons in a lead nucleus. Why doesn’t the lead nucleus burst apart? 1) Coulomb repulsive force doesn’t act inside the nucleus 2) gravity overpowers the Coulomb repulsive force inside the nucleus 3) the negatively charged neutrons balance the positively charged protons 4) protons lose their positive chargeinside the nucleus 5) none of the above

25. What weighs more, an electron and a proton, or a hydrogen atom? 1) electron and proton 2) hydrogen atom 3) both the same ConcepTest 30.2a Binding Energy I

26. What weighs more, an electron and a proton, or a hydrogen atom? 1) electron and proton 2) hydrogen atom 3) both the same ConcepTest 30.2a Binding Energy I less The total energy (or mass) of a hydrogen atom must be less than the energies (or masses) of the electron plus the proton individually in order for the electron to be bound.

27. ConcepTest 30.2b Binding Energy II What is the total energy (or mass) of the hydrogen atom in its ground state? 1) 13.6 eV 2) m p c 2 + m e c 2 + 13.6 eV 3) m p c 2 + m e c 2 4) m p c 2 + m e c 2 – 13.6 eV

28. less The mass difference is the binding energy. The total energy (or mass) of a hydrogen atom must be less than the energies (or masses) of the electron plus the proton individually in order for the electron to be bound. The mass difference is the binding energy. ConcepTest 30.2b Binding Energy II What is the total energy (or mass) of the hydrogen atom in its ground state? 1) 13.6 eV 2) m p c 2 + m e c 2 + 13.6 eV 3) m p c 2 + m e c 2 4) m p c 2 + m e c 2 – 13.6 eV

29. 1) the 2 neutrons and 1 proton 2) the tritium nucleus 3) they both weigh the same 4) it depends on the specific isotope of tritium On a balance scale, you put 2 neutrons and 1 proton on one side and you put a tritium nucleus ( 3 H) on the other. Which side weighs more? ConcepTest 30.2c Binding Energy III

30. less The mass difference is the binding energy. The mass of the 2 neutrons and 1 proton is less when they are bound together as tritium. The mass difference is the binding energy. need to add 8.5 MeV to balance scale 1) the 2 neutrons and 1 proton 2) the tritium nucleus 3) they both weigh the same 4) it depends on the specific isotope of tritium On a balance scale, you put 2 neutrons and 1 proton on one side and you put a tritium nucleus ( 3 H) on the other. Which side weighs more? ConcepTest 30.2c Binding Energy III

31. 1) removing a proton takes more energy 2) removing a neutron takes more energy 3) both take the same amount of energy Does it take more energy to remove one proton or one neutron from 16 O? ConcepTest 30.3 Separation Energy

32. less repulsive Coulomb force Removing a proton takes less energy because the repulsive Coulomb force between positively charged protons helps to push the proton out of the nucleus. Remember that neutrons are uncharged. 1) removing a proton takes more energy 2) removing a neutron takes more energy 3) both take the same amount of energy Does it take more energy to remove one proton or one neutron from 16 O? ConcepTest 30.3 Separation Energy

33. A radioactive nucleus undergoes gamma decay. How large would you expect the energy of the emitted photon to be? 1) less than 13.6 eV 2) 13.6 eV 3) hundreds of eV 4) millions of eV 5) billions of eV ConcepTest 30.5 Radioactive Decay Energy

34. several MeV The binding energy of nuclei is of the order several MeV (millions of eV). So, we would expect the energy of gamma decay to be in the same ballpark. A radioactive nucleus undergoes gamma decay. How large would you expect the energy of the emitted photon to be? 1) less than 13.6 eV 2) 13.6 eV 3) hundreds of eV 4) millions of eV 5) billions of eV ConcepTest 30.5 Radioactive Decay Energy Follow-up: What process could release a photon with billions of eV?

35. 1) the 234 Th nucleus 2) the alpha particle 3) both the same A uranium nucleus 238 U (initially at rest) decays into a thorium nucleus 234 Th and an alpha particle. Which one has the greater momentum? ConcepTest 30.6a Alpha Decay I

36. same initial momentum was zero By momentum conservation, they must have the same magnitude of momentum since the initial momentum was zero. 1) the 234 Th nucleus 2) the alpha particle 3) both the same A uranium nucleus 238 U (initially at rest) decays into a thorium nucleus 234 Th and an alpha particle. Which one has the greater momentum? ConcepTest 30.6a Alpha Decay I Follow-up: In what directions are the two products emitted?

37. 1) the 234 Th nucleus 2) the alpha particle 3) both the same ConcepTest 30.6b Alpha Decay II A uranium nucleus 238 U (initially at rest) decays into a thorium nucleus 234 Th and an alpha particle. Which one has the greater velocity?

38. 1) the 234 Th nucleus 2) the alpha particle 3) both the same thesame smaller masslarger velocity The momentum is mv and is the same for both, but the alpha particle has the smaller mass, so it has the larger velocity. ConcepTest 30.6b Alpha Decay II A uranium nucleus 238 U (initially at rest) decays into a thorium nucleus 234 Th and an alpha particle. Which one has the greater velocity?

39. 1) the 234 Th nucleus 2) the alpha particle 3) both the same ConcepTest 30.6c Alpha Decay III A uranium nucleus 238 U (initially at rest) decays into a thorium nucleus 234 Th and an alpha particle. Which one has the greater kinetic energy?

40. 1) the 234 Th nucleus 2) the alpha particle 3) both the same momentum is thesame smaller masslarger KE The kinetic energy 1/2 mv 2 can be written as KE = p 2 /2m. The momentum is the same for both, but the alpha particle has the smaller mass, so it has the larger KE. ConcepTest 30.6c Alpha Decay III A uranium nucleus 238 U (initially at rest) decays into a thorium nucleus 234 Th and an alpha particle. Which one has the greater kinetic energy?

41. What element results when 14 C undergoes beta decay? 1) 1) 15 C 2) 2) 15 N 3) 3) 14 C 4) 14 N 5) 15 O ConcepTest 30.7 Beta Decay

42. The reaction is: What element results when 14 C undergoes beta decay? 1) 1) 15 C 2) 2) 15 N 3) 3) 14 C 4) 14 N 5) 15 O n  p + e - + changing a neutron into a proton Z increases by 1 Inside the nucleus, the reaction n  p + e - + has occurred, changing a neutron into a proton, so the atomic number Z increases by 1. However the mass number (A = 14) stays the same. ConcepTest 30.7 Beta Decay Follow-up: How would you turn 14 C into 15 N?

43. You have 16 kg of a radioactive sample with a certain half-life of 30 years. How much is left after 90 years? (1) 8 kg (2) 4 kg (3) 2 kg (4) 1 kg (5) nothing ConcepTest 30.8a Radioactive Decay Law I

44. 90 years3 half-lives After three half-lives  2 kg left The total time (90 years) is 3 half-lives. After one half-life  8 kg left. After two half-lives  4 kg left. After three half-lives  2 kg left. You have 16 kg of a radioactive sample with a certain half-life of 30 years. How much is left after 90 years? (1) 8 kg (2) 4 kg (3) 2 kg (4) 1 kg (5) nothing ConcepTest 30.8a Radioactive Decay Law I Follow-up: When will the sample be reduced to nothing?

45. You have 12 kg of a radioactive substance. Ten years later, you find that you only have 3 kg left. Find the half-life of the material. (1) 20 years (2) 10 years (3) 7.5 years (4) 5 years (5) 2.5 years ConcepTest 30.8b Radioactive Decay Law II

46. total time is 10 years half-life must be 5 years After one half-life  6 kg left. After two half-lives  3 kg left. So if the total time is 10 years, then the half-life must be 5 years. (2 half-lives = 10 years) You have 12 kg of a radioactive substance. Ten years later, you find that you only have 3 kg left. Find the half-life of the material. (1) 20 years (2) 10 years (3) 7.5 years (4) 5 years (5) 2.5 years ConcepTest 30.8b Radioactive Decay Law II Follow-up: How much of the sample is left after another 10 years?

47. You have 400 g of a radioactive sample with a half-life of 20 years. How much is left after 50 years? 1) more than 100 g 2) 75 - 100 g 3) 75 g 4) 50 - 75 g 5) less than 50 g ConcepTest 30.8c Radioactive Decay Law III

48. You have 400 g of a radioactive sample with a half-life of 20 years. How much is left after 50 years? Total time (50 years) is 2 1/2 half-lives. After one half-life  200 g left After two half-lives  100 g left. After three half-lives  50 g left. So after 2 1/2 half-lives  75 g left ? So after 2 1/2 half-lives  75 g left ? No!! No!! Exponential function is not linear! 70.7 g left  70.7 g left N = N o e –(0.693 / T 1/2 )t 1) more than 100 g 2) 75 - 100 g 3) 75 g 4) 50 - 75 g 5) less than 50 g ConcepTest 30.8c Radioactive Decay Law III

49. You have two samples, A (T 1/2 = 10 yr) and B (T 1/2 = 20 yr) with initially different amounts. The initial amount of sample A is 64 kg, while the amount of sample B is unknown. If you observe that the 2 amounts are equal after 40 years, what is the initial amount of B? 1) 64 kg 2) 32 kg 3) 16 kg 4) 8 kg 5) 4 kg ConcepTest 30.8d Radioactive Decay Law IV

50. 4 half-lives4 kg 2 half-lives16 kg For sample A, after 40 years (4 half-lives), there is 4 kg left. Now work backwards from there, for sample B: 40 years is 2 half-lives, so sample B initially had 16 kg. You have two samples, A (T 1/2 = 10 yr) and B (T 1/2 = 20 yr) with initially different amounts. The initial amount of sample A is 64 kg, while the amount of sample B is unknown. If you observe that the 2 amounts are equal after 40 years, what is the initial amount of B? 1) 64 kg 2) 32 kg 3) 16 kg 4) 8 kg 5) 4 kg ConcepTest 30.8d Radioactive Decay Law IV Follow-up: When will the samples again have equal amounts?

51. You have 10 kg each of a radioactive sample A with a half-life of 100 years, and another sample B with a half-life of 1000 years. Which sample has the higher activity? 1) sample A 2) sample B 3) both the same 4) impossible to tell ConcepTest 30.9a Activity and Half-Life I

52. shorter half-life decays more quickly higher activity If a sample has a shorter half-life, this means that it decays more quickly (larger decay constant ) and therefore has a higher activity: that is sample A. In this case, that is sample A. You have 10 kg each of a radioactive sample A with a half-life of 100 years, and another sample B with a half-life of 1000 years. Which sample has the higher activity? 1) sample A 2) sample B 3) both the same 4) impossible to tell ConcepTest 30.9a Activity and Half-Life I  N/  t = – N Follow-up: What is the ratio of activities for the two samples?

53. The same amount of two different radioactive samples A and B is prepared. If the initial activity of sample A is 5 times larger than that of sample B, how do their half- lives compare? 1) T 1/2 of A is 5 times larger than B 2) half-lives are the same 3) T 1/2 of A is 5 times smaller than B ConcepTest 30.9b Activity and Half-Life II

54. larger activitydecays more quicklyshorter half-life A larger activity means that a sample decays more quickly, and this implies a shorter half-life. The same amount of two different radioactive samples A and B is prepared. If the initial activity of sample A is 5 times larger than that of sample B, how do their half- lives compare? 1) T 1/2 of A is 5 times larger than B 2) half-lives are the same 3) T 1/2 of A is 5 times smaller than B ConcepTest 30.9b Activity and Half-Life II

55. What is the Q-value for radioactive decay reactions? 1) Q < 0 2) Q > 0 3) Q = 0 4) sign of Q depends on the nucleus ConcepTest 31.1 Nuclear Reactions

56. spontaneously releaseenergy exothermicQ-value is positive Radioactive decay happens spontaneously, because the nucleus can reach a lower energy state. Thus, such reactions can only occur spontaneously if they release energy (exothermic ), so the Q-value is positive. What is the Q-value for radioactive decay reactions? 1) Q < 0 2) Q > 0 3) Q = 0 4) sign of Q depends on the nucleus ConcepTest 31.1 Nuclear Reactions Follow-up: Is radioactive decay an endothermic or exothermic reaction?

57. ConcepTest 31.2 Nuclear Reaction Products What is the nucleus that results in the reaction given below? O 17 8 O 15 7 N 7 F 7 1)2)3)4) X A Z

58. Add up the totals for nucleons (A) and protons (Z) separately, and see what you need to balance both sides: Nucleons: 1 + 16 = x + 2  x = 15 Protons: 0 + 8 = y + 1  y = 7 The missing nucleus has A = 15 and Z = 7. ConcepTest 31.2 Nuclear Reaction Products What is the nucleus that results in the reaction given below? O 17 8 O 15 7 N 7 F 7 1)2)3)4) X A Z Follow-up: What would you get if you started with p + 16 O instead?

59. What element results when 14 C undergoes beta decay? 1) 1) 15 C 2) 2) 15 N 3) 3) 14 C 4) 14 N 5) 15 O ConcepTest 31.3 Beta Decay Products X A Z

60. The reaction is: Essentially, a neutron turns into a proton (emitting a  – particle), so the atomic number Z of the nucleus must increase by one unit, but without changing the atomic mass A. What element results when 14 C undergoes beta decay? 1) 1) 15 C 2) 2) 15 N 3) 3) 14 C 4) 14 N 5) 15 O ConcepTest 31.3 Beta Decay Products X A Z

61. How does the total mass of the fission fragments compare to the mass of the original nucleus in a fission reaction? 1) fission fragments have more mass 2) fission fragments have less mass 3) fission fragments have the same mass ConcepTest 31.4 Nuclear Fission

62. fission reaction releases energy must be less The fission reaction releases energy, so the total energy (or mass) of the fission fragments must be less than the energy (or mass) of the original nucleus. How does the total mass of the fission fragments compare to the mass of the original nucleus in a fission reaction? 1) fission fragments have more mass 2) fission fragments have less mass 3) fission fragments have the same mass ConcepTest 31.4 Nuclear Fission Follow-up: Where are the fission fragments located relative to the original nucleus on the curve of binding energy per nucleon?

63. How does the binding energy per nucleon of a fusion product compare to that of the pieces that combined to form it? 1) product has greater BE than the pieces 2) product has less BE than the pieces 3) product has the same BE than the pieces ConcepTest 31.5 Nuclear Fusion

64. fusion reaction releases energy product is more tightly bound binding energy per nucleon is greater for the fusion product The fusion reaction releases energy, so the product is more tightly bound (more stable) than the separate pieces that combined to form it. This means that the binding energy per nucleon is greater for the fusion product. How does the binding energy per nucleon of a fusion product compare to that of the pieces that combined to form it? 1) product has greater BE than the pieces 2) product has less BE than the pieces 3) product has the same BE than the pieces ConcepTest 31.5 Nuclear Fusion Follow-up: Which weighs more: the fusion product or the pieces?

65. Which type of radiation goes farther in matter before losing all of its energy ? 1) alpha radiation 2) beta radiation 3) gamma radiation 4) all about the same distance ConcepTest 31.6 Radiation Shielding

66.    paperaluminumlead Alpha particles have such a large charge, they ionize many atoms in a short distance, and so lose their energy rapidly and stop. Gamma rays travel great distances before ionizing an atom. Which type of radiation goes farther in matter before losing all of its energy ? 1) alpha radiation 2) beta radiation 3) gamma radiation 4) all about the same distance ConcepTest 31.6 Radiation Shielding

67. Curly is twice as far from a small radioactive source as Moe. Compared to Curly’s position, the intensity of the radiation (and therefore exposure) at Moe’s position is about: 1) one-quarter 2) one-half 3) the same 4) double 5) quadruple CurlyMoe radioactive source ConcepTest 31.7a Radiation Exposure I

68. obeys the inverse square lawTwice as close means 4 times the intensity A small source can be treated as a point source and so it obeys the inverse square law of intensity. Twice as close means 4 times the intensity (and therefore exposure). Curly is twice as far from a small radioactive source as Moe. Compared to Curly’s position, the intensity of the radiation (and therefore exposure) at Moe’s position is about: 1) one-quarter 2) one-half 3) the same 4) double 5) quadruple CurlyMoe radioactive source ConcepTest 31.7a Radiation Exposure I

69. Curly is working 5 m from a highly radioactive source and must reduce his exposure by at least a factor of 10. Assuming that an inverse square law (1/r 2 ) applies in this case, to what distance should he move? 1) 7.5 m 2) 10 m 3) 15 m 4) 20 m 5) 50 m Curly radioactive source ConcepTest 31.7b Radiation Exposure II

70. obeys the inverse square law15 m reduces the exposure by 9 times 20 mfactor of 16 reduction A small source can be treated like a point source and so it obeys the inverse square law of intensity. Moving to 15 m (3 times farther) only reduces the exposure by 9 times. He has to move farther away (20 m) in order to get a factor of 16 reduction, which meets the “safety limit” of 10 times. Curly is working 5 m from a highly radioactive source and must reduce his exposure by at least a factor of 10. Assuming that an inverse square law (1/r 2 ) applies in this case, to what distance should he move? 1) 7.5 m 2) 10 m 3) 15 m 4) 20 m 5) 50 m Curly radioactive source ConcepTest 31.7b Radiation Exposure II

71. Radiation can damage matter such as metals or biological tissue by: 1) heating up the material 2) causing cancer in the metal 3) producing fission reactions in the material 4) removing electrons from the atoms 5) producing fusion reactions in the material ConcepTest 31.8 Radiation Damage

72. Radiation can ionize the atoms in matter, which means knocking out electrons. Metals become brittle and cell processes can be disrupted. Radiation can damage matter such as metals or biological tissue by: 1) heating up the material 2) causing cancer in the metal 3) producing fission reactions in the material 4) removing electrons from the atoms 5) producing fusion reactions in the material ConcepTest 31.8 Radiation Damage Follow-up: What type of radiation will tend to do the most damage?