Nuclear Physics and Radioactivity Peta Konsep Fisika Nuklir The evolution of the universe An approximate timeline for the evolution of the universe from the Big Bang to the present.

In the liquid drop model of nuclear fission, the uranium nucleus is split into two lighter nuclei by a high-energy neutron. In a U-235 fission chain reaction, the fission of the uranium nucleus produces high-energy neutrons that go on to split more nuclei. The energy released in this process can be used to produce electricity.

A nuclear reactor uses the energy produced in the fission of U-235 to produce electricity. Energy from a nuclear fission reaction produces hot, high-pressure steam that turns a turbine. As the turbine turns, electricity is produced. Some Nuclear Units Relative scale model of an atom and the solar system

Do you perceive a gold ring to contain a larger fraction of solid matter than the solar system? Data for Scale Model of Atom Simbol dan Struktur Atom Ukuran Inti Atom 15

1 3 r (1,2 10 m)(A ) 4 3 V r 3 Ukuran inti atom. Estimasi diameter inti atom berikut ini:40

1 208 H Ca Pb 20 82 (a)1 (b) (c) Penyelesaian: (a) untuk H : d=(2r)(A1/3)=2,4 10-15 m

(b) untuk calsium : 15 1 3 15 d (2,4 10 m)(40 ) 8,2 10 m

SOME PROPERTIES OF NUCLEI the atomic number Z, which equals the number of protons in the nucleus, the neutron number N, which equals the number of neutrons in the nucleus, the mass number A, which equals the number of nucleons in the nucleus (nucleon is a generic term used to refer to either a proton or a neutron). Radioactivity Abdus Salam Pakistani physicist Abdus Salam won the 1979 Nobel Prize in physics. He won the award for his work in developing a unification hypothesis

concerning electromagnetic and weak interactions between atomic particles. Pierre Curie (French physicist) Peluruhan Alpha (Alpha Decay) Peluruhan Beta (Beta Decay) Sinar Gamma (Gamma Ray) Alpha, Beta, and

Gamma Historically, the products of radioactivity were called alpha, beta, and gamma when it was found that they could be analyzed into three distinct species by either a magnetic field or an Penetration of

Matter Though the most massive and most energetic of radioactive emissions, the alpha particle is the shortest in range because of its strong interaction with matter. The electromagnetic gamma ray is extremely penetrating, even penetrating considerable thicknesses of

Isotop Atoms of the same element that differ in mass number are called isotopes 1993-2003 Microsoft Corporation. All rights reserved. Isotopes The different isotopes of a given element have the same atomic number but different mass numbers since they have different numbers of neutrons. The chemical properties of the different isotopes of an element are identical, but they will often have great differences in nuclear stability. For stable isotopes

light elements, the number of neutrons will be almost equal to the number of protons, but a growing neutron excess is characteristic of stable heavy elements. The element tin (Sn) has the most stable isotopes with 10, the average being about 2.6 stable isotopes per element. Radioactive HalfLife The radioactive half-life for a given radioisotope is the time for half the radioactive nuclei in any sample to undergo radioactive decay. After two half-lives, there will be one fourth the original sample, after three halflives one eight the original sample, and so forth.

Radioactivity Equations dN N dt dN dt N N N 0e t

Laju peluruhan dN t t A N N 0 e A0 e dt Radioactivity Equations A A0 e

t A0 A 2 t T1 2 T1

T A0 1 T 2 A0 e e e 2 2 2

T 0,693 ln(e ) ln(2) T 1 2 1 2 1 2

1 2 Carbon Dating Presuming the rate of production of carbon-14 to be constant, the activity of a sample can be directly compared to the equilibrium activity of living matter and the age calculated.

Various tests of reliability have confirmed the value of carbon data, and many examples provide an interesting range of application. Carbon-14 decays with a half life of about 5730 years by the emission of an electron of energy 0.016 MeV. This changes the atomic number of the nucleus to 7, producing a nucleus of nitrogen-14. At equilibrium with the atmosphere, a gram of carbon shows an activity of about 15 decays per

minute. Carbon Dating The low activity of the carbon-14 limits age determinations to the order of 50,000 years by counting techniques. That can be extended to perhaps 100,000 years by accelerator techniques for counting the carbon-14 concentration. Origin of carbon-14

Radiocarb on (C-14) Dating Radiocarbon (C-14) Dating All living organisms absorb radiocarbon, an unstable form of carbon that has a half-life of about 5,730 years. During its lifetime, an organism continually replenishes its supply of radiocarbon by breathing and eating. After the organism dies and becomes a fossil, C-14 continues to decay without being replaced. To measure the amount of radiocarbon left in a fossil, scientists burn a small piece to convert it into carbon dioxide gas. Radiation counters are used to detect the

electrons given off by decaying C-14 as it turns into nitrogen. The amount of C-14 is compared to the amount of C-12, the stable form of carbon, to determine how much radiocarbon has decayed and to date the fossil.Encarta Encyclopedia Microsoft Corporation. All Rights Reserved 1993-2003 Microsoft Corporation. All rights reserved. Radioactive Dating The age of an object made from once-living matter, such as wood, can be determined using the natural radioactivity of 14C. All living plants absorb carbon dioxide (CO 2) from the air and use it to synthesize organic molecules.

The vast majority of these carbon atoms are 126C, but small fraction, about 1.3 x 10-12, is the radioactive isotope 14C, with a half-life of about 5730 yr. The Iceman On 19 September 1991, German tourists on a walking in the Italian Alps found a Stone Age traveler, later called the Iceman, whose body had become trapped in a glacier. Material found with the body had a 14C activity of about 0,121 per gram of carbon. Find the age of the Icemans remains.

Reasoning: The number of nuclei remaining at the time t is : t N N0e Multiplying both sides of this expression by the decay constant and recognizing that the product of and N is the activity A, we find: t 0

Where A0=0.23 Bq is the activity at time t=0 for one gram of carbon. The decay constant can be determined from the value of 5730 yr from the half-life of C-14. With known value for A0 and , the given activity of A=0.121 Bq per gram of carbon can be used to find t, the Icemans age. A A e Solution: For C-14, the decay constant is : 0.693 / T12 0.693 /(5730 yr) 1.2110-4 yr-1

Since A=0.121 Bq ana A0=0.23 Bq, the age can be determine from: A 0.121 Bq (0.23 Bq) e (1.2110 4 yr -1 ) t Taking the natural logarithm of both sides of this result gives: 0.121 Bq 4 -1

ln (1.2110 yr )t 0.23 Bq We gives an age for the sample of: t 5300 yr Contoh: Isotop 14C mempunyai waktu paroh 5730 th. Jika pada suatu saat di sebuah sampel terdapat 1.00x1022 atom Carbon14. Berapakah aktivitas sampel tersebut?

0.693 0.693 12 -1 3 . 832 10

s 7 T1 (5730 th)(3.15610 s/th) 2 N 12 -1 22 A N (3.83210 s )(1.00 10 ) t

N 10 N A 3 . 832 10 decays/s t 10 A 3 . 832 10 peluruhan/ s