NUCLEAR PHYSICS
1. Radius of atom is about 5 times the radius of nucleus
2. Nucleus consists of nucleons(protons and neutrons)
3. A proton has a positive charge equals to 1.6×10-19C
4. Atomic no. = no. Of protons = Z
5. Atomic mass = p + n = A
6. In initial light elements n = p
7. In heavy elements n > p
8. Stability depends upon no. of neutron
9. 1amu = 1.67 × 10-27kg = 931 Mev
10. 1amu = mass of C-12/12
11. An atom on the whole is electrically neutral
12. Binding energy is the amount of energy that must be supplied to a nucleus if nucleus is to be broken up into protons and neutrons
13. B.E/nucleon = mass defect × c²/A
14. Mass defect = Zmp + (A-Z) mn - mnucleus
15. B.E/nucleon ist increases then decreases
16. B.E/nucleon is maximum for Fe-58 = 8.8Mev
17. B.E/nucleon is minimum for U-238 = 7.6Mev
18. Iron is most stable element
19. B.E for deutron = 2.23MeV = 1.2×10-¹²J
20. B.E for tritium = 7.97MeV
21. B.E for Helium = 28.2 MeV
22. Beta particle is a fast moving e- that come out of nucelus
23. Beta decay oocurs when n/p ratio is too high
24. Alpha decay occurs when n/p ratio is too low
25. Alpha and beta emission occurs when nucleus undergoes excitation
26. Gama decay occurs when nucleus undergoes dexcitation
27. Radioactivity is purely a nuclear phenomenon. This is not affected by chemical or physical reaction
28. During nuclear changes, law of conservation of mass, energy, momentum and charge remains applicable
29. In alpha decay, mass no. And charge no. both are decreases by 4 and 2 respectively
30. Emission of alpha particle from radium-226 gives radon-222
31. In beta decay, mass no. does not change while charge no. is increased by 1.
32. The emission of beta particle from Polonium-218 gives Astatine-218
33. The emission of beta particle from Thorium-234 gives Protactinium-234
34. Emission of alpha particle from uranium-238 gives Thorium-234
35. Gama radiation is simply a photon that has neither any charge nor any mass. So no change in mass no. and charge no. will occur with its emission
36. Radioactive decay process is quite random so we cannot tell about any particular atom as to when will it decay
37. Decay rate is inversly proportional to half-life
38. Activity is directly proportional to half-life A=λN (here λ is decay constant)
39. Decay constant is directly proportional to no. of decaying atoms. Delta N = - λN t
40. Unit of decay constant is s-¹
41. Mean life > Half life
42. Mean life = 1/λ
43. λT½ = 0.693
44. T½ = Tmean (0.693/λ)
45. No. of half lifes = Total time/half life
46. Undecayed = N°/2n (here n is power of 2)
47. Decayed = total - undecayed
48. Example 21.2
49. Half life of
Radon = 3.8 days
U-239 = 23.5 mint
U-238 = 4.5×109 years
I-131 = 8 days
I-125 = 60 days
Np = 2.4 days
Pu = 24000 years
Na-24 = 15 hours
Fe-59 = 45 days
50. Range of beta particle is 100 times greater than alpha particle
51. Ionizing ability of beta particle is 100 times less than alpha particle
52. Alpha particle is about 7000 times massive than an e- thats why it does not suffer appreciable deflection from its straight path
53. At energy less than 0.5MeV, photoelectric effect is dominant
54. At energy more than 1.02MeV, pair production is dominant
55. Intensity of gama rays falls off as the inverse square of distance from source
56. 𝐠 −particle ionizes an atom due to electrostatic attraction and due to direct elastic collision
57. Typical source of alpha particle is Radon-222
58. Typical source of beta particle is Strontium-94
59. Typical source of gama rays is Cobalt-60
60. Gamma rays are absorbed by lead sheet.
61. Gamma rays are more penetrating as compared to alpha and beta particle
62. Neutrons are more penetrating than gamma rays
63. Ionizing ability of alpha particle > beta particle > gamma rays > neutrons
64. He+² is an alpha particle
65. Only alpha particles emit with same energy while beta particles and gamma rays emit with variable energy
66. When alpha particle strikes with 7N-14 then we get one proton and 8O-17
67. In nuclear fission, 1MeV/nucleon energy is released
68. In nuclear fusion, 6.4MeV/nucleon energy is released
69. U-235 : naturally occuring 0.7%. usually fissionable with thermal neutron or slow neutron. % increase in fuel 2-4%
70. Plutonium-239 : fission with Slow neutron is easy
71. U-238 = 99%
72. fission chain reaction is controlled by cadmium rod because these rods are capable of absorbing large no. Of neutrons
73. Now-a-days Plutonium-239 and Uranium-233 are also being used as fuel
74. In nuclear reaction, heavy water is used as moderator to slow down neutrons
75. No. of neutrons are controlled by Cadmium or boron rods in nuclear reactor
76. For fission reactions, ratio of mass of products to mass of reactants is less than 1
77. Fast reactors are designed to make use of U-238 which is about 99%
78. Plutonium can be fissioned by fast neutron
79. Moderators are not needed in fast reactors
80. Do U Know?
U-238..... >U-238..... >Np..... >Pu
This sequence follows emission of gamma, beta+gamma, beta+gamma. 3 gamma 2 beta particles
81. When two deutrons are merged to form a helium nucleus, 24MeV energy is released
82. When deutron and tritium are merged, 17.6MeV energy is releaed
84. Subatomic particles are divided into three groups
a. Photons
b. Leptons (e-, muons)/do not experience strong nuclear force
c. Hadrons (n, mesons, p)/experience strong nuclear force
85. Meson = 1Quark and 1Antiquark
86. Meson mass equal or greater than protons
87. Baryon = 3 Quarks
88. Baryon mass lighter than protons
89. Proton = 2up Quarks + 1down Quark
90. Neutron = 1up Quark + 2 down Quark
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