14. nuclear physics

7/21/2019 14. Nuclear Physics

1/19

Leaving Cert Physics Long Questions: 14.Nuclear Physics

Please remember to photocopy 4 pages onto one sheet by going A3A4 and using back to back on the photocopier

2014 - 2002

Solutions (to higher level questions only) begin on page13

The Atom

2008 Question 10 [r!inary Leve"#

Give two properties of an electron.

The diagram shows the arrangement used by utherford to investigate the structure of the atom. !uring the

investigation he fired alpha"particles at a thin sheet of gold foil in a vacuum.

(i) #hat are alpha"particles$

(ii) !escribe what happened to the alpha"particles during the

e%periment.

(iii) #hat conclusion did utherford ma&e about thestructure of the atom$

(iv)'ow are the electrons arranged in the atom$

(v) ame a device used to detect alpha"particles.

(vi)#hy was it necessary to carry out this e%periment in a vacuum$

2011 Question 12 $!% [r!inary Leve"#

The diagram shows the arrangement used to investigate the structure of the atom. !uring the investigation

alpha"particles were fired at a thin sheet of gold foil in a

vacuum.

(i) #hat are alpha"particles$(ii) #hat happened to the alpha"particles in the

e%periment$

(iii) #hat did the e%periment reveal about the structure

of the atom$

(iv)ame the scientist who designed the e%periment.

(v) ame a suitable detector of alpha"particles.

2002 Question 12 $!%

(i) The diagram shows a simplified arrangement of an e%periment

carried out early in the *+thcentury to investigate the structureof the atom.

ame the scientist who carried out this e%periment.

(ii) !escribe what was observed in this e%periment.

(iii) #hy was it necessary to carry out this e%periment in a

vacuum$

(iv)#hat conclusion did the scientist form about the structure of the atom$

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&a!ioactivity

2010 Question 12 $!% [r!inary Leve"#

(i) #hat is radioactivity$

(ii) The diagram shows a shielded radioactive source emitting nuclear

radiation.

'ow do you &now that the source is emitting three types of

radiation$

(iii) ame the radiation bloc&ed by each material.

(iv)Give one danger associated with nuclear radiation.

(v) State two precautions that should be ta&en when handling radioactive substances.

(vi)Give two uses for radioactive substances



(ii) ame the ,rench physicist who discovered radioactivity in 1-/.

(iii) The diagram illustrates that three types of radiation are emitted from a

radioactive source.ame the radiations labelled (i) 0 (ii) (iii) 2 in the diagram.

(iv)#hich one is the most ionising$

(v) ame a detector of ionising radiation.

(vi)utline the principle on which the detector wor&s.

(vii) Great care has to be ta&en when dealing with radioactive sources.

Give4

(i) two precautions that should be ta&en when dealing with radioactive sources5

(ii) one use of a radioactive source5

(iii) one harmful effect of radiation.

2


3/19


The world6s most devastating nuclear accident happened at 7hernobyl in the 8&raine in 1-/. 9n the early

hours of the morning of */ :pril of that year there were two loud e%plosions that blew the roof off and

completely destroyed the o. ; reactor releasing during the course of the following days / to < tonnes of

radioactive material with a total activity of about 1+1-becquerels into the atmosphere.

The discharge included over a hundred radioisotopes but iodine and caesium isotopes were of main

relevance from a human health and environmental point of view. 7ontamination in the surrounding areas

was widespread with the half"life of some of the materials measured in thousands of years.

=arge numbers of people involved in the initial clean up of the plant received average total body radiation

doses of about 1++ mSv " about five times the ma%imum dose permitted for wor&ers in nuclear facilities.

:verage worldwide total body radiation dose from natural >bac&ground6 radiation is about *.; mSv annually.

!uring and soon after the accident and the initial clean"up at least 3+ plant personnel and firefighters died

from burns and radiation. 9n the eight years following the accident a further 3++ suffered radiation sic&ness

and there are possible lin&s between the accident and increased numbers of thyroid cancers in neighbouring

regions.

(:dapted from ?@hysics A a teacher6s handboo&B !ept. of Cducation and Science.)

(i) #hat is meant by a nuclear accident$

(ii) The o. ; reactor was a fission reactor. #hat is nuclear fission$(iii) ame two parts of a nuclear fission reactor.

(iv)#hat is measured in becquerels$

(v) Give two e%amples of radioisotopes.

(vi)#hat is meant by the half"life of a substance$

(vii) #hat is meant by bac&ground radiation$

(viii) Give two effects of radiation on the human body.

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4/19

200' Question 11 [r!inary Leve"#

ead this passage and answer the questions below. adon is a naturally occurring radioactive gas. 9t

originates from the decay of uranium which is present in small quantities in roc&s and soils. adon is

colourless odourless and tasteless and can only be detected using special equipment li&e a Geiger"DEller

tube that can measure the radiation it releases. Fecause it is a gas radon can move freely through the soil

and enter the atmosphere. #hen radon reaches the open air it is quic&ly diluted to harmless concentrations

but when it enters an enclosed space such as a house it can sometimes accumulate to unacceptably high

concentrations. adon can enter a building from the ground through small crac&s in floors and through gaps

around pipes and cables. adon is drawn from the ground into a building because the indoor air pressure is

usually lower than outdoors. Feing radioactive radon decays releasing radiation.

#hen radon is inhaled into the lungs the radiation released can cause damage to the lung tissue.

(a) #hat is radioactivity$

(b) #hat is the source of radon$

(c) ame a detector of radiation.

(d) 'ow does radon enter a building$

(e) 'ow can the build"up of radon in the home be prevented$

(f) #hy is radon dangerous$

(g) #hy is radon harmless in the open air$

(h) ame a radioactive element other than radon.


adon is a radioactive gas which emits alpha particles. adon gas comes into houses through gaps in the

floors. C%posure to radon gas can cause lung cancer


(ii) ame the other two types of radiation emitted by radioactive sources.

(iii) !escribe an e%periment to distinguish between the three types of radiation.

(iv)=ist three properties of one of these radiations.

(v) The most stable isotope of radon has a half"life of ; days.

#hat are isotopes$

(vi)#hy is it important to prevent radon gas entering your home$

(vii) 9f no more radon gas entered your home how long would it be until one eight of the radon gas was

left$

(viii) Give two uses of radioisotopes.

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(a")-"i)e

200* Question 12 $!% [r!inary Leve"#

a*H is a radioactive isotope of sodium. 9t has a half life of 1 minute.

(i) #hat is meant by radioactivity$

(ii) ame a detector of radioactivity.

(iii) C%plain the term half life.

(iv)#hat fraction of a sample of a*H remains after 3 minutes$

(v) Give one use of a radioactive isotope.

200' Question 12 $!%

(i) C%plain the term half"life.

(ii) : sample of carbon is mainly carbon"1* which is not radioactive and a small proportion of carbon"1;

which is radioactive. #hen a tree is cut down the carbon"1; present in the wood at that time decays by

beta emission.

#rite a nuclear equation to represent the decay of carbon"1;.

(iii) :n ancient wooden cup from an archaeological site has an activity of *.1 Fq.

The corresponding activity for newly cut wood is -.; Fq.

9f the half"life of carbon"1; is H


6/19


9n the manufacture of newsprint paper heavy rollers are used to adIust the thic&ness of the moving paper.

The paper passes between a radioisotope and a detector and a pair of rollers as shown.

The radioisotope used is Sr"+ and it emits beta"particles which are recorded by the detector. The output

from the detector adIusts the gap between the rollers so that the paper is of uniform thic&ness.

(i) ame a suitable detector.

(ii) !escribe how the reading on the detector may vary as the paper passes by.

(iii) #hy would the radioisotope :m"*;1 which emits alpha"particles notbe suitable for this process$

(iv)7alculate the number of atoms present in a sample of Sr"+ when its activity is ;*H+ Fq.

The half"life of Sr"+ is *-.


7/19

201+ Question ,

(i) !efine the becquerel.

(ii) ame one device used to detect ionising radiations.

(iii) 7ompare alpha beta and gamma emissions using the following headings4 (a)penetrating ability (b)

deflection in a magnetic field.

The photograph shows one of the nuclear reactors at 7hernobyl where there was a fire in :pril 1-/ that

released large quantities of radioactive contaminants.

:mong the contaminants were iodineA131 and caesiumA13


8/19

ission an! usion

uc"ear &eactors


(i) #hat is meant by radioactivity$

(ii) 9n an e%periment the radiation from a radioactive source is passed through an electric field as shown in

the diagram.

#hat does this e%periment indicate about radiation$

(iii) #hich type of radiation is unaffected by electric fields$

(iv)#hich type of radiation is positively charged$

(v) #hich type of radiation is negatively charged$

(vi)Give the name of radiation types 1 * and 3 in that order.

(vii) uclear fission occurs in a nuclear power station.

ame a suitable fuel for nuclear fission.

(viii) C%plain the role of neutrons in nuclear fission.

(i%)C%plain how the control rods can control the rate of fission or stop the reaction

completely.

(%) 9odineA131 is a product of nuclear fission. The half"life of iodineA131 is - days.

#hat fraction of iodineA131 remains after *; days$

201+ Question 12 $!% [r!inary Leve"#

(i) uclear fission occurs in the reactor of a nuclear power station li&e the

one shown in the photograph.

#hat is nuclear fission$

(ii) ame a fuel used in a nuclear reactor.

(iii) 'ow can the reaction in a nuclear reactor be controlled$

(iv)'ow is the energy produced in a reactor used to generate electricity$

(v) State a haKard of nuclear reactors.

200/ Question , [r!inary Leve"#

The diagram shows a simple nuclear fission reactor.

Cnergy is released in a fission reactor when a chain reaction occurs in the

fuel rods.

(i) #hat is meant by fission$ ame a material in which fission occurs.

(ii) !escribe how a chain reaction occurs in the fuel rods.

(iii) C%plain how the chain reaction is controlled.

(iv)#hat is the purpose of the shielding$

(v) ame a material that is used as shielding.

(vi)!escribe what happens to the coolant when the reactor is wor&ing.(vii) Give one effect of a nuclear fission reactor on the environment.

(viii) Give one precaution that should be ta&en when storing radioactive materials.

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ead this passage and answer the questions below.

The ,u&ushima nuclear disaster

9n Darch *+11 following a powerful earthqua&e the ,u&ushima

nuclear reactor in Lapan was shut down automatically.

: nuclear reactor generates heat by splitting atoms of uranium in a

process &nown as nuclear fission.

The uranium is contained in the reactor6s fuel rods. : chain reaction

is set up by the neutrons released during fission and these go on to

split more atoms of uranium.

The power output of the reactor is adIusted by controlling the

number of neutrons that are present. 7ontrol rods made of a neutron

absorber capture neutrons.

:bsorbing more neutrons in a control rod means that there are fewer

neutrons available to cause fission. Therefore pushing the control rods deeper into the reactor will reduce its

power output and e%tracting the control rods will increase it.

The ,u&ushima nuclear reactor continued to generate heat even after the chain reaction was stopped becauseof the radioactive decay of the isotopes created during nuclear fission. This decay cannot be stopped and the

resulting heat must be removed by circulating cooling water through the reactor core.

#hen the reactor was shut down due to the earthqua&e the pumps to &eep the cooling water circulating

should have been powered by electricity from the national grid or diesel generators. 'owever connections

to the grid were damaged by the earthqua&e and the diesel generators were destroyed by the tsunami wave

that followed the earthqua&e. :s a result no cooling was available for the reactor core and this resulted in

the e%plosions and subsequent release of radiation consisting of radioactive isotopes such as caesium and

iodine into the environment.

(:dapted from >#i&ipediaM Lune *+11)

(a) #hat is meant by nuclear fission$(b) #hat is radioactivity$

(c) #hat is a nuclear chain reaction$

(d) #hat is the function of the control rods$

(e) #hat type of material are control rods made of$

(f) #hy did the reactor still generate heat even though the chain reaction had stopped$

(g) #hy is it important to remove the heat generated$

(h) Give one advantage of nuclear energy.

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200+ Question 10 [r!inary Leve"#


(ii) The diagram shows the basic structure of a nuclear reactor.

(iii) : nuclear reactor contains (i) fuel rods (ii) control

rods (iii) moderator (iv) heat e%changer.

(iv)Give the function of any two of these.

(v) 9n a nuclear reactor energy is released by nuclear fission

when a chain reaction occurs.

(vi)#hat is nuclear fission$

(vii) #hat is a chain reaction$

(viii) Thic& shielding is placed around a nuclear reactor because of the penetrating power of the radiation

emitted.

ame three types of radiation that are present in a nuclear reactor.

(i%)ame an instrument used to detect radiation.

(%) @lutonium is produced in a nuclear reactor. 9t is a highly radioactive substance with a very long half"life.

#hen the fuel in a nuclear reactor is used up the fuel rods are reprocessed to remove the plutonium.

(%i)Give two precautions that are ta&en when storing the plutonium.

200, Question 10 [r!inary Leve"#

adioactive elements are unstable and decay with the release of radiation.

(i) 'ow would you detect radiation$

(ii) ame the three types of radiation.

(iii) #hich radiation is negatively charged$

(iv)#hich radiation has the shortest range$

(v) #hich radiation is not affected by electric fields$

(vi)uclear fission occurs in a nuclear reactor.

(vii) #hat is nuclear fission$

(viii) #hat is the role of neutrons in nuclear fission$

(i%)ame a fuel used in a nuclear reactor.(%) 9n a nuclear reactor how can the fission be controlled or stopped$

(%i)'ow is the energy produced in a nuclear reactor used to generate electricity$

(%ii) Give one advantage and one disadvantage of a nuclear reactor as a source of energy.

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(igher Leve"

2014 Question 8

: nuclear reactor is a device in which a sustained chain reaction ta&es place.

,rom each nuclear fission only one (on average) of the emitted neutrons hits another nucleus to cause

another fission. The power output from a sustained nuclear reaction doesn6t grow but is constant.

(i) C%plain the underlined terms.

(ii) : substance called a moderator is mi%ed with the fuel in a nuclear reactor.

7ontrol rods are used to control the rate of the reaction.

Give an e%ample of a moderator.

(iii) C%plain why a moderator is needed in a nuclear reactor

(iv)C%plain how the control rods affect the rate of the reaction.

(v) : heat e%changer is used in a nuclear reactor.

C%plain how the heat e%changer operates.

(vi)#hy is it necessary to use a heat e%changer$

(vii) @lutonium is produced in a fission reactor when one of the neutrons released in the fission reaction

converts uraniumA*3- into plutoniumA*3 with the emission of two beta"particles.

#rite an equation for this nuclear reaction.

(viii) Cach fission of a uraniumA*3H nucleus produces *+* DeN of energy.

nly 3HO of this energy is used to generate electricity.'ow many uraniumA*3H nuclei are required to undergo fission to generate a constant electric power of 1

G# for a day$

2008 Question 12 $c%

(i) 9n 13 =ise Deitner discovered that the uranium isotope 8A*3- undergoes fission when struc& by a

slow neutron. FariumA13 and &ryptonA< nuclei are emitted along with three neutrons.

#rite a nuclear reaction to represent the reaction.

(ii) 9n a nuclear fission reactor neutrons are slowed down after being emitted.

#hy are the neutrons slowed down$

(iii) 'ow are they slowed down$(iv),ission reactors are being suggested as a partial solution to 9reland6s energy needs.

Give one positive and one negative environmental impact of fission reactors.

2010 Question 12 $%

The following reaction occurs in a nuclear reactor4

U+ 235

n Ba141

0

1 +X+3 n+202.5MeV01

(i) 9dentify the element 0.

(ii) 7alculate the mass difference between the reactants and the products in the reaction(iii) #hat is a chain reaction$

(iv)Give one condition necessary for a chain reaction to occur.

(v) Give one environmental impact associated with a nuclear reactor.

2012 Question 8

Cnergy can be produced in a fusion reaction by combining a deuterium and a tritium nucleus as follows4

H+ H13

1

2 He+n+energy2

4

(i) !istinguish between nuclear fission and nuclear fusion.

11


12/19

(ii) #hat are the advantages of fusion over fission in terms of fuel sources and

reaction products$

(iii) 'ow much energy is produced when a deuterium nucleus combines with

a tritium nucleus$

(iv)7alculate the force of repulsion between a deuterium and a tritium nucleus

when they are * nm apart in free space.

(v) ,usion can only ta&e place at very high temperatures. C%plain why.

200/ Question 8

(i) !istinguish between fission and fusion.

(ii) The core of our sun is e%tremely hot and acts as a fusion reactor.

#hy are large temperatures required for fusion to occur$

(iii) 9n the sun a series of different fusion reactions ta&e place. 9n one of the reactions * isotopes of

helium each with a mass number of 3 combine to form another isotope of helium with the release of *

protons.

#rite an equation for this nuclear reaction.

(iv)7ontrolled nuclear fusion has been achieved on earth using the following reaction4

H+ H13

1

2 He+ n0

1

2

4

#hat condition is necessary for this reaction to ta&e place on earth$

(v) 7alculate the energy released during this reaction.

(vi)Give one benefit of a terrestrial fusion reactor under each of the following headings4

(a) fuel5 (b) energy5 (c) pollution.

speed of light P *.- J 1+A-m sA15 mass of hydrogen"* nucleus P 3.3;* J 1+A*


13/19

o"utions to (igher Leve" uestions

2014 Question 8

$i% 35"ain the un!er"ine! terms.

: self"sustaining reaction Q a reaction where the release of one or more neutrons causes further fission.

,ission is the splitting of a large nucleus into two (smaller) nuclei with the release of energyQneutrons.

(ii) 6ive an eam5"e o) a mo!erator.

graphite Q (heavy) water

(iii) 35"ain 7hy a mo!erator is nee!e! in a nuc"ear reactor

to slow down neutrons Q so as to increase the probability of fission.

(iv)35"ain ho7 the contro" ro!s a))ect the rate o) the reaction.

Fy absorbing neutrons

(v) 35"ain ho7 the heat echanger o5erates.

heatQenergy from reactor transfers to liquidQwater in heat e%changer (to drive a turbine)

(vi)hy is it necessary to use a heat echanger9

the material in a reactor is radioactive Q allows the core to reach a higher temperature

(vii) rite an euation )or this nuc"ear reaction.

U92238+n0

1 Pu94

239+210

(viii) (o7 many uranium2+* nuc"ei are reuire! to un!ergo )ission to generate a constant e"ectric5o7er o) 1 6 )or a !ay9

Cach fission P (*+* J1+/)(1./ J 1+A1) Q 3.*3 J 1+A11L

3HO of *+* DeN P 1.13 J 1+A11L

1 G# for a day P -./; J 1+13L


14/19

2012 Question 8

$i% ;istinguish et7een nuc"ear )ission an! nuc"ear )usion.

,ission4 large nucleus splits into two smaller nuclei (of similar siKe)

,usion4 two small nuclei Ioin to form a larger nucleus

$ii% hat are the a!vantages o) )usion over )ission in terms o) )ue" sources an! reaction 5ro!ucts9

(hydrogen) fuel (from the sea) is plentiful A (uranium for fission is scarce)

no radioactive waste with fusion A (fission results in radioactive waste)

$iii% (o7 much energy is 5ro!uce! 7hen a !euterium nuc"eus comines 7ith a tritium nuc"eus9

eactants4 *.+1;1+* 3.+1/+; P H.+3+1H1

@roducts4 ;.++*/+3 1.++-/


15/19


$i% ame a suita"e !etector.

GD tube (lin&ed with a ratemeterQscaler)Q Solid state detector

$ii% ;escrie ho7 the rea!ing on the !etector may vary as the 5a5er 5asses y.

The count rate would decrease with increasing paper thic&ness.

$iii% hy 7ou"! the ra!ioisoto5e Am-241< 7hich emits a"5ha-5artic"es< not e suita"e )or this

5rocess9

The alpha"particles have poor penetrating power so would be easily bloc&ed by the paper.

$iv%Ca"cu"ate the numer o) atoms 5resent in a sam5"e o) r-,0 7hen its activity is 42*0 >.

The ha")-"i)e o) r-,0 is 28.'8 years.

1 year P 3/H days 3/H.*H days

TUP +./3 Q

P +./3Q T1Q* P


16/19

9ts half life is very short (with respect to age of the universe) and because it is not a member of a decay

series it is not produced >in nature6 (it is created artificially).

16


17/19

2008 Question 12 $c%

(i) rite a nuc"ear reaction to re5resent the reaction.

$ii% ?n a nuc"ear )ission reactor< neutrons are s"o7e! !o7n a)ter eing emitte!. hy are the neutrons

s"o7e! !o7n9

nly slow neutrons cause fission.

$iii% (o7 are they s"o7e! !o7n9

They collide with the molecules in the moderator.

$iv%ission reactors are eing suggeste! as a 5artia" so"ution to ?re"an!Bs energy nee!s.

6ive one 5ositive an! one negative environmenta" im5act o) )ission reactors.

@ositive4 no 7*emissions Q no greenhouse gases Q less dependence on fossil fuels.

egative4 radioactive waste Q potential for maIor accidents etc.

200' Question 12 $!%

$i% 35"ain the term ha")-"i)e.

Time for half the radioactive nuclei in a sample to decay

(ii) rite a nuc"ear euation to re5resent the !ecay o) caron-14.$iii% ?) the ha")-"i)e o) caron-14 is *'+0 years< estimate the age o) the

cu5.

-.; Fq to *.1 Fq requires two half"lives.

:nswer P11;/+ years

$iv%ame an instrument use! to measure the activity o) a sam5"e.

Geiger Duller tube.

$v% hat is the 5rinci5"e o) o5eration o) this instrument9

The gas is ionised and a pulse of chargeQcurrent flows.

200/ Question 8$i% ;istinguish et7een )ission an! )usion.

uclear ,ission is the brea&"up of a large nucleus into two smaller nuclei with the release of energy (and

neutrons).

uclear ,usion is the combining of two small nuclei to form one large nucleus with the release of

energy.

$ii% hy are "arge tem5eratures reuire! )or )usion to occur9

uclei are positively charged so enormous energy is required to overcome the very large repulsion.

$iii% rite an euation )or this nuc"ear reaction.

$iv%hat con!ition is necessary )or this reaction to ta=e 5"ace on earth9Nery large energyQtemperature is necessary .

$v% Ca"cu"ate the energy re"ease! !uring this reaction.

Dass of reactants P -.3;/ % 1+"*


18/19

200* Question 8

$i% ;istinguish et7een ra!ioactivity an! )ission.

uclear ,ission is the brea&"up of a large nucleus into two smaller nuclei with the release of energy (and

neutrons).

uclear ,usion is the combining of two small nuclei to form one large nucleus with the release of

energy.

$ii% 6ive an a55"ication o) ra!ioactivity.

Smo&e detectors carbon dating tracing lea&s cancer treatment sterilising etc.

$iii% 6ive an a55"ication o) )ission.

Generating electrical energy bombs

$iv%&a!ioactivity causes ionisation in materia"s. hat is ionisation9

9onisation occurs when a neutral atom loses or gains an electron.

$v% ;escrie an e5eriment to !emonstrate the ionising e))ect o) ra!ioactivity.

:pparatus4 radioactive source and charged (gold leaf) electroscope

@rocedure4 bring radioactive source close to the cap

bservation4 leaves collapse

7onclusion4 charge lea&s away through ionised air Q electroscope neutralised by ionised air

$vi%rite an euation to re5resent the !ecay o) coa"t/0.

$vii% Ca"cu"ate the !ecay constant o) coa"t/0.

,ormula4 T1Q* P ln *Q P T1/2Qln *T1/2 P H.*/ y P 1.// J 1+

-s and ln * P +./3

P 1.// J 1+-Q+./3 Z P ;.1- J 1+"s"1

$viii% Ca"cu"ate the rate o) !ecay o) a sam5"e o) coa"t/0 7hen it has 2.* 1021atoms.

dQdt P (")

P (;.1- J 1+")( *.H J 1+*1) P 1.+; J 1+13Fq

200+ Question 11

$a% hat is ra!ioactive !ecay9adioactivity is the brea&up of unstable nuclei with the emission of one or more types of radiation.

$% hat is an isoto5e9

9sotopes are atoms which have the same :tomic umber but different Dass umbers.

$c% A5art )rom Dcaron !atingE< give t7o other uses o) ra!ioactive isoto5es.

Dedical imaging (battery of) heart pacema&ers steriliKation tracers irradiation of food &illing cancer cells

measuring thic&ness smo&e detectors nuclear fuel

$!% (o7 many neutrons are in a 14C nuc"eus9

Cight

$e% 14C !ecays to 14. rite an euation to re5resent this nuc"ear reaction.1;

/7 [

14. nuclear physics

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