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Makalah Fisika Nuklir
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Bahan Matrikulasi
Fisika (III): Fisika Inti
Oleh
Dedi Setiabudidaya
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Periodic Table of the Elements
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Some questions about the atom
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Atoms the historical view
The Greek Empedocle (around 492-432 BC.) divided matter into four elements, that he also called "roots": earth, air, fire and waterThe word "atom" comes from the greek "a-tomos" and signifies "indivisible". This notion was invented by Leucippe of Milet in 420 BCProgram Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Each electron orbital has a different shape, and no two electrons can be in the same orbital (unless they have opposite spins.)
The quantum rules for the electron orbitals in an atom determine the row structure in the periodic table. The geometry of the electron orbitals determines the structure of an atomProgram Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Some questions:
What is an element?Why are nuclei and atoms stable?What is a molecule?Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Parts of an Atom
Each element in the Periodic Table has a different number of protons in its nucleusProtons have positive chargeChange the number of protons change elements This is called nuclear physics The element also has the same number of electronsElectrons have negative chargeChange the number of electrons ionize the element This is called chemistry Some elements also have neutrons Neutrons have no chargeThey are in the nuclei of atomsProgram Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
The Hydrogen Atom
One electron orbiting a nucleus
1 proton = Z = atomic number
0 neutrons = N
Total mass = A = Z+N =1
Singly ionized Hydrogen is missing one electron = 1H+
Add a neutron and you have Deuterium = 2H = D
1H
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
p
e
The Helium Atom
Two electrons orbiting a nucleus
2 protons = Z = atomic number
2 neutrons = N
Total mass = A = Z+N =4
Singly ionized Helium is missing one electron = 4He+
Doubly ionized Helium is missing both electrons = a particle = 4He++
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
p
p
n
n
e
e
4He
Isotopes and Elements
If Helium loses one of its neutrons, it becomes an isotope3He
3H (Tritium)
If Helium loses one of its protons (and one of its electrons), it becomes a different elementProgram Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
p
n
n
e
p
p
n
e
e
Radioactivity ("Activity")
Definition: A collection of unstable atoms that undergo spontaneous transformation that result in new elements. An atom with an unstable nucleus will decay until it becomes a stable atom, emitting radiation as it decaysSometimes a substance undergoes several radioactive decays before it reaches a stable stateThe amount of radioactivity (called activity) is given by the number of nuclear decays that occur per unit time (decays per minute).Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Types of Radiation
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Mass
(amu)
Charge
Travel Distance in Air
Alpha
Beta Plus
Beta Minus
Gamma
X-Rays
Neutron
4.0000
0.0005
0.0005
0.0000
0.0000
1.0000
+2
+1
-1
0
0
0
few centimeters
few meters
few meters
many meters
many meters
many meters
Interaction of Radiation with Matter
Radiation deposits small amounts of energy, or "heat" in matteralters atomschanges moleculesdamage cells & DNAsimilar effects may occur from chemicalsMuch of the resulting damage is from the production of ion pairsProgram Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Exposure and Dose
Exposure is ionization in air and is measured in Roentgen (R) or coulomb/kg (C/kg)1 R = 2.58 10-4 C/kgAbsorbed dose is the energy absorbed by a material and is measured in rad or gray (Gy)1 rad = 100 erg/g1 gray = 1 joule/kg1 gray = 100 rad1 rad (in air) = 0.87 RProgram Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Dosimetry System
Dose equivalent (H) is a measure of the biological damage caused by radiationH = D Q ND = absorbed dose (in a tissue or organ)
Q = quality factor
(Q for and = 1, Q for = 20)
N = other modifying factors (N = 1)
Dose equivalent measured in rem or sievert (Sv)Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Dosimetry System
Effective dose equivalent (He)He = wT HT
HT = Dose equivalent in tissue or organ T
wT = Weighting factor for tissue or organ T
wT used to account for the different sensitivities of tissues and organs to radiationEffective dose equivalent also measured in rem or sievert (Sv)Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
TissuewTGonads0.25Breast0.15Red bone marrow0.12Lung0.12Thyroid0.03Bone surfaces0.03Remainder0.30Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Absorbed
Dose (Rads)
Effect
10,000
1,200
600
450
100
50
25
5
Death in a few hours
Death within days
Death within weeks
LD 50/30
Probable Recovery
No observable effect
Blood changes definite
1st Blood change obs
Annual Dose from Background Radiation (US)
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Total US average dose equivalent = 360 mrem/year
Radon
Internal 11%
Cosmic 8%
Terrestrial 6%
Man-Made 18%
55.0%
Medical X-Rays
Nuclear
Medicine 4%
Consumer
Products 3%
Other 1%
11
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya
Program Studi Pengelolaan Lingkungan
Program Pascasarjana Universitas Sriwijaya