Physics Project 1

7/25/2019 Physics Project 1

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Project

OnRADIOACTIVITY


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CERTIFICATE

This is to certify that of class XII has

completed the physics projectentitledRADIOACTIVITY herself and ndermy !idance" The pro!ress of theproject has #een continoslyreported and has #een in my

$no%led!e consistently"


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Radioactivity:

Radioactivity is the decay or disintegration of the nucleusof a radioactive element. The radiation emitted is the

alpha-particles, the beta-particles and the gamma rays

and a lot of heat. This phenomenon as !rst discovered

by a French "hysicist, #enri $ec%uerel in &'(). *ther

famous people parts of this radioactive era are+ ord

Rutherford, and the Curie couple, arie and "ierre.

Radioactive decay is a stochastic i.e., random/ process at

the level of single atoms, in that, according to %uantum

theory, it is impossible to predict hen a particular atom

ill decay. #oever, the chance that a given atom ill

decay is constant over time.


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A diagram shoing an alpha particle / being e0ected

from the nucleus of an atom. "rotons are red and

neutrons are blue.

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&'C()'R'*+DI+COV'RY


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In arch of &'(), during a time of overcast

eather, $ec%uerel found he couldnt use the sunas an initiating energy source for his eBperiments.

#e put his rapped photographic plates aay in a

darened draer, along ith some crystals

containing uranium. uch to his $ec%uerels

surprise, the plates ere eBposed during storage

by invisible emanations from the uranium. The

emanations did not re%uire the presence of an

initiating energy source--the crystals emitted rays

on their onD Although $ec%uerel did not pursue

his discovery of radioactivity, others did and, in so

doing, changed the face of both modern medicine

and modern science. #e as a member of a

scienti!c family eBtending through severalgenerations, the most notable being his

grandfather Antoine-Csar $ec%uerel &>''&'>'/,


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his father, AleBandre-Edmond $ec%uerel &'9@(&/,

and his son Gean $ec%uerel. &'>'&(


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ability to turn air into a conductor of electricity. The

Curies found that the pitchblende produced a

current :@@ times stronger than that produced by

pure uranium. They tested and recalibrated theirinstruments, and yet they still found the same

puling results. The Curies reasoned that a very

active unnon substance in addition to the

uranium must eBist ithin the pitchblende. In the

title of a paper describing this hypothesied

element hich they named polonium after ariesnative "oland/, they introduced the ne termJ

Hradio-active.H

After much grueling or, the Curies ere able to

eBtract enough polonium and another radioactive

element, radium, to establish the chemical

properties of these elements. arie Curie, ith herhusband and continuing after his death,

established the !rst %uantitative standards by

hich the rate of radioactive emission of charged

particles from elements could be measured and

compared. In addition, she found that there as a

decrease in the rate of radioactive emissions overtime and that this decrease could be calculated

and predicted. $ut perhaps arie Curies greatest

and most uni%ue achievement as her realiation

that radiation is an atomic property of matter


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rather than a separate independent emanation.

"olish-born French physicist, famous for her or

on radioactivity and tice a inner of the 1obel

"rie. =ith #enri $ec%uerel and her husband, "ierreCurie, she as aarded the &(@: 1obel "rie for

"hysics. 2he as the sole inner of the &(&& 1obel

"rie for Chemistry. 2he as the !rst oman to in

a 1obel "rie, and she is the only oman to in the

aard in to diKerent !elds.

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In &(&&, Rutherford conducted a series of

eBperiments in hich he bombarded a piece of

gold foil ith positively charged alpha/ particles

emitted by radioactive material. ost of the

particles passed through the foil undisturbed,

suggesting that the foil as made up mostly of

empty space rather than of a sheet of solid atoms.2ome alpha particles, hoever, Hbounced bac,H

indicating the presence of solid matter. Atomic

particles, Rutherfords or shoed, consisted

primarily of empty space surrounding a ell-

de!ned central core called a nucleus.

In a long and distinguished career, Rutherford laidthe groundor for the determination of atomic

structure. In addition to de!ning the planetary

model of the atom, he shoed that radioactive


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elements undergo a process of decay over time.

And, in eBperiments hich involved hat

nespapers of his day called Hsplitting the atom,H

Rutherford as the !rst to arti!cially transmuteone element into another--unleashing the

incredible poer of the atom hich ould

eventually be harnessed for both bene!cial and

destructive purposes.

Ta$en to!ether, the %or$ of

&ec-erel, the Cries, Rtherford

and others, made modern medical

and scienti.c research more than

a dream" They made it a reality

%ith many applications" A loo$ atthe se of isotopes re/eals jst

some of the %ays in %hich the


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pioneerin! %or$ of these

scientists has #een tili0ed"

RADIATIO1+

&. Alpha-particlesJThis type of radiation is positivelycharged. It is relatively massive. It has a lo

penetrating poer. It5s about &-9@thas fast as light. It

is eBactly lie the helium atom.

9.$eta-particlesJThis type of radiation is negativelycharged but can also be Lvely charged/. It is

relatively light. It is about as fast as light. They arehigh energy electrons. It has a medium penetrating

poer.


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:. Mamma RaysJ This radiation is neutral in charge.#as a very high penetrating poer. It is at the speed

of light. It is an electromagnetic ave ith very short

avelength. It is very light.

TYP'+ O2

RADIOACTIVITY


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I" 1AT)RA* RADIOCTIVITY

This is the type of radioactivity hich consists of a

spontaneous decay of the radioactive nucleus. Thephenomenon is eBperienced by naturally

radioactive substances. The radiation might come

out individually or combined and, as alays, ith a

lot of energy.

2ome radioactive substances areJ

Americim 345674sed in many smoe detectors forhomes and business. To measure levels of toBic lead in

dried paint samples. To ensure uniform thicness in rolling

processes lie steel and paper production and to help

determine here oil ells should be drilled.

Cadmim 368974sed to analye metal alloys for

checing stoc, sorting scrap.

Calcim 3 5:7Important aid to biomedical researchers

studying the cell functions and bone formation of

mammals.

Californim 3 4;474sed to inspect airline luggage for

hidden eBplosives...to gauge the moisture content of soil

in the road construction and building industries...and to

measure the moisture of materials stored in silos.

Car#on 3 657#elps in research to ensure that potential

ne drugs are metabolied ithout forming harmful by-

products.


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Cesim 3 6


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ere both successfully treated for Mraves disease, a

thyroid disease, ith radioactive iodine./

Iridim 3 69474sed to test the integrity of pipeline

elds, boilers and aircraft parts.

Iron 3 ;;74sed to analye electroplating solutions.

>rypton 3 ?;74sed in indicator lights in appliances lie

clothes asher and dryers, stereos and coKee maers. To

gauge the thicness of thin plastics and sheet metal,

rubber, teBtiles and paper. And to measure dust and

pollutant levels.

1ic$el 3 =


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+elenim 3 :;74sed in protein studies in life science

research.

+odim 3 4574sed to locate leas in industrial pipelines.

And in oil ell studies.

+trontim 3 ?;74sed to study bone formation and

metabolism.

Technetim 3 99m7The most idely used radioactive

isotope for diagnostic studies in nuclear medicine.

6iKerent chemical forms are used for brain, bone, liver,

spleen and idney imaging and also for blood No

studies.

Thallim 3 4857easures the dust and pollutant levels

on !lter paper...and gauges the thicness of plastics,

sheet metal, rubber, teBtiles and paper.

Thoriated tn!sten74sed in electric are elding rods inthe construction, aircraft, petrochemical and food

processing e%uipment industries. It produces easier

starting, greater arc stability and less metal

contamination.

Thorim 3 4497#elps Nuorescent lights to last longer.

Thorim 3 4


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luminous dials, gauges and rist atches and to produce

luminous paint.

)ranim 3 4


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II. ARTIFICIA RA6I*ACTI7IT8

In this radioactivity, normally unreactive elements aremade reactive by bombarding them ith radiation. Curieand Goliot shoed that hen lighter elements suchas boron and aluminum ere bombarded ith -particles,there as a continuous emission of radioactive radiations,even after the source had been removed. They shoedthat the radiation as due to the emission of a particlecarrying one unit positive charge ith mass e%ual to thatof an electron.

1eutron activation is the main form of inducedradioactivity, hich happens hen free neutrons arecaptured by nuclei. This ne heavier isotope can bestable or unstable radioactive/ depending onthe chemical element involved. $ecause free neutronsdisintegrate ithin minutes outside of anatomic nucleus, neutron radiation can be obtained onlyfrom nuclear disintegrations, nuclear reactions, and high-

energy reactions such as in cosmic radiation shoersor particle accelerator collisions/. 1eutrons that havebeen sloed don through a neutron moderator thermalneutrons/ are more liely to be captured by nuclei thanfast neutrons.

A less common form involves removing a neutronvia photodisintegration. In this reaction, a high energyphoton gamma ray/ stries a nucleus ith energygreater than the binding energy of the atom, releasing aneutron. This reaction has a minimum cutoK of9 e7 for deuterium/ and around &@ e7 for most heavynuclei. any radionuclides do not produce gamma raysith energy high enough to induce this reaction.


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The isotopes used in food irradiation cobalt-)@, caesium-&:>/ both have energy peas belo this cutoK and thuscannot induce radioactivity in the food.

2ome induced radioactivity is produced by bacgroundradiation, hich is mostly natural. #oever, since naturalradiation is not very intense in most places on Earth, theamount of induced radioactivity in a single location isusually very small.

The conditions inside certain types of nuclearreactors ith high neutron NuB can cause inducedradioactivity. The components in those reactors maybecome highly radioactive from the radiation to hichthey are eBposed. Induced radioactivity increases theamount of nuclear aste that must eventually bedisposed, but it is not referred to as radioactivecontamination unless it is uncontrolled.


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)ni/ersal la% of

radioacti/e decay

Radioactivity is one very fre%uent eBample of eBponential decay.

The la describes the statistical behavior of a large number of

nuclides, rather than individual ones. In the folloing formalism,

the number of nuclides or nuclide population N, is of course adiscrete variable a natural number/Obut for any physical

sample Nis so large amounts of LP &@9:, Avogadros constant/

that t can be treated as a continuous variable. 6iKerential

calculus is needed to set up diKerential e%uations for modeling

the behavior of the nuclear decay.


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*ne-decay process

Consider the case of a nuclideAdecaying into another Bby some

processA Bemission of other particles, lie electron

neutrinos

e and electrons ein beta decay, are irrelevant in hat follos/.

The decay of an unstable nucleus is entirely random and it is

impossible to predict hen a particular atom ill decay. #oever,

it is e%ually liely to decay at any time. Therefore, given a sample

of a particular radioisotope, the number of decay

events dNeBpected to occur in a small interval of time dtis

proportional to the number of atoms present N, that is

"articular radionuclides decay at diKerent rates, so each has its

on decay constant . The eBpected decay dNQNis

proportional to an increment of time, dtJ

The negative sign indicates that Ndecreases as time

increases, as each decay event follos one after another.

The solution to this !rst-order diKerential e%uation is

the functionJ

=here N@is the value of Nat time tP @.

=e have for all time tJ


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=here Ntotalis the constant number of particles

throughout the decay process, clearly e%ual to the

initial number ofAnuclides since this is the initialsubstance.

If the number of non-decayedAnuclei isJ

Then the number of nuclei of B, i.e. number of

decayedAnuclei, is

#AF-IFE


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Miven a sample of a particular radionuclide, the half-life is the

time taen for half the radionuclides atoms to decay. For the case

of one-decay nuclear reactionsJ

The half-life is related to the decay constant as follosJ set N =

N0/2and tP T&Q9to obtain

This relationship beteen the half-life and the decay constant

shos that highly radioactive substances are %uicly spent, hile

those that radiate ealy endure longer. #alf-lives of non

radionuclides vary idely, from more than &@ years, such as for

the very nearly stable nuclide 9@($i, to &@9:seconds for highly

unstable ones.

The factor of ln 9/ in the above relations results from the fact that

concept of Hhalf-lifeH is merely a ay of selecting a diKerent base

other than the natural base e for the lifetime eBpression. The time

constant

is the e-& -life, the time until only &Qeremains, about:).', rather than the


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the same proportionof a given radioactive substance ill decay,

during any time-period that one chooses.

athematically, the nthlife for the above situation ould be found

in the same ay as aboveOby setting N = N0/n, SSS& andsubstituting into the decay solution to obtain

*CC4RRE1CE I11AT4RE

According to the $ig $ang theory, stable isotopes of thelightest !ve elements #, #e, and traces of i, $e, and $/ere produced very shortly after the emergence of theuniverse, in a process called $ig $ang nucleosynthesis.These lightest stable nuclides including deuterium/survive to today, but any radioactive isotopes of the light


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elements produced in the $ig $ang such as tritium/ havelong since decayed. Isotopes of elements heavier thanboron ere not produced at all in the $ig $ang, and these!rst !ve elements do not have any long-lived

radioisotopes. Thus, all radioactive nuclei are, therefore,relatively young ith respect to the birth of the universe,having formed later in various other types ofnucleosynthesis in stars in particular, supernovae/, andalso during ongoing interactions beteen stable isotopesand energetic particles. For eBample, carbon-&;, aradioactive nuclide ith a half-life of only :@ years, isconstantly produced in Earths upper atmosphere due to

interactions beteen cosmic rays and nitrogen.

1uclides that are produced by radioactive decay arecalled radiogenic nuclides, hether they themselvesare stable or not. There eBist stable radiogenic nuclidesthat ere formed from short-lived eBtinct radionuclides inthe early solar system. The eBtra presence of these stableradiogenic nuclides such as Ue-&9( from primordial I-

&9(/ against the bacground of primordial stablenuclides can be inferred by various means.Radioactive primordial nuclides found in the Earth areresidues from ancient supernova eBplosions hichoccurred before the formation of the solar system. Theyare the long-lived fraction of radionuclides surviving inthe primordial solar nebula through planet accretion untilthe present. The naturally occurring short-lived radiogenic radionuclides found in rocs are thedaughters of these radioactive primordial nuclides.Another minor source of naturally occurring radioactivenuclides are cosmogenic nuclides, formed by cosmic raybombardment of material in theEarths atmosphere or crust. The radioactive decay of


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these radionuclides in rocs ithinEarths mantle and crust contribute signi!cantlyto Earths internal heat budget.

D'T'CTIO1 O2

RADIATIO1+6" )+I1@ A DO+I'T'R OR A 2I* &AD@'7A dosimeter is a

device orn by radioactive orers. It is basically a !lm hich

darens on incidence of radiation. It is used to no the level

of radiation the orer has been eBposed to.


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4" A @'I@'R CO)1T'R7This consists of a Meiger-uller tube

hich consists of a ire/, a scaleQrate meter, and often a

loudspeaer. The alls of the container acts as the cathode

hile the central ire acts as the anode. The radiation enters

through a thin indo. Each particle or ray ionies several gas

atoms. Ions attracted to the cathode, electrons to the anode.*ther atoms are hit on the ay creating an avalanche of more

ions and electrons. The loudspeaer ampli!es a clic sound for

each pulse shoing the randomness of the decay.


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)+'+ O2

RADIOACTIVITY

6" Radiolo!y7 This is sed for research and stdy in the

medical .eld"

4" Radiotherapy7 This is sed in the treatment ofdiseases, especially cancer"6ue to the penetrating poer

of gamma rays, they are used to collectively and controllably

destroy malignant cells.


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5" @amma3Radio!raphyJ This is the production of a special

type of photograph, a radiograph. It is used for %uality control

in industries. The maing of a radiograph re%uires some type

of recording mechanism. The most common device is !lm. A

radio!raphis actually a photographic recording produced bythe passage of radiation through a sub0ect onto a !lm,

producing hat is called a latent image of the sub0ect.

;" Radiocar#on or car#on datin!7All living matter contains

carbon-&; absorbed from the atmosphere. This radioactive

element has a half-life of about


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:" Other ses of radioacti/ityJ 2teriliation of medical

instruments and food is another common application ofradiation. $y sub0ecting the instruments and food to

concentrated beams of radiation, e can ill microorganisms

that cause contamination and disease. $ecause this is done

ith high energy radiation sources using electromagnetic

energy, there is no fear of residual radiation. Also, the

instruments and food may be handled ithout fear of

radiation poisoning.

Radiation sources are eBtremely important to themanufacturing industries throughout the orld. They are

commonly employed by nondestructive testing personnel to

monitor materials and processes in the maing of the

products e see and use every day. Trained technicians use

radiography to image materials and products much lie a

:" 1clear reactorsaredevices that control !ssion

reactions producing ne

substances from the !ssion

product and energy. 1uclear

poer stations use uranium

in !ssion reactions as a fuel

to produce energy. 2team is

generated by the heat

released during the !ssion

process. It is this steam that


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dentist uses radiation to B-ray your teeth for cavities. There

are many industrial applications that rely on radioactivity to

assist in determining if the material or product is internally

sound and !t for its application.

#A?AR62 *F

RA6I*ACTI7E

24$2TA1CE2


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The dangers of radioactivity and radiation ere not immediately

recognied. The discovery of U-rays in &'(< led to ide spread

eBperimentation by scientists, physicians, and inventors. any

people began recounting stories of burns, hair loss and orse in

technical 0ournals as early as &'(). In February of that year,

"rofessor 6aniel and 6r. 6udley of 7anderbilt4niversity performed an eBperiment involving B-raying 6udleys

head that resulted in him losing hair under here the tube as

placed reported in the The X-rays Sciencenes supplement/. A

report by 6r. #.6. #as, a graduate of Columbia College, of his

suKering severe hand and chest burns in an B-ray demonstration,

as the !rst of many other reports inElectrical Revie. any

eBperimenters including Elihu Thomson at Thomas Edisons

lab, =illiam G. orton, and 1iola Tesla also reported burns. Elihu

Thomson deliberately eBposed a !nger to an B-ray tube over a

period of time and suKered pain, selling, and blistering. *ther

eKects ere sometime blamed for the damage including

ultraviolet rays and according to Tesla/ oone. any physicians

claimed there ere no eKects form B-ray eBposure at all.


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The genetic eKects of radiation, including the eKect of cancer ris,

ere recognied much later. In &(9>, #ermann Goseph

uller published research shoing genetic eKects, and in &(;)

as aarded the 1obel "rie for his !ndings.

$efore the biological eKects of radiation ere non, many

physicians and corporations began mareting radioactive

substances as patent medicine in the form of glo-in-the-dar

pigments. EBamples ere radium enema treatments, and radium-

containing aters to be drun as tonics. arie Curie protested

this sort of treatment, arning that the eKects of radiation on the

human body ere not ell understood. Curie later died

from aplastic anemia, liely caused by eBposure to ioniing

radiation. $y the &(:@s, after a number of cases of bone necrosis

and death of enthusiasts, radium-containing medicinal products

had been largely removed from the maret radioactive

%uacery/.


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&I&*IO@RAPEY

6" 1C'RT Physics TeFt#oo$ for class XII4" %%%"%i$ipedia"or!

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Physics Project 1