matriculation physics radioactivity.pdf

8/12/2019 Matriculation Physics Radioactivity.pdf

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1

PHYSICS CHAPTER 15

is defined as the spontaneousis defined as the spontaneousdisintegration of certaindisintegration of certain

atomic nuclei accompanied byatomic nuclei accompanied by

the emission of alphathe emission of alpha

particles, beta particles orparticles, beta particles or

gamma radiation.gamma radiation.

CHAPTER 15: RadioactivityCHAPTER 15: Radioactivity(3 Hours)(3 Hours)


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PHYSICS CHAPTER 15

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At the end of this chapter, students should be able to:At the end of this chapter, students should be able to:

ExplainExplain,,++,,andand decays.decays. StateStatedecay law and usedecay law and use

DefineDefineactivity,activity,AAand decay constant,and decay constant, .. Derive and useDerive and use

DefineDefinehalf-life andhalf-life and useuse

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ics 15.1 Radioactiv# d#cay (% "ours)

Ndt

dN=

teNN

= 0t

eAA = 0!"!"

2ln

2/1 =T


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PHYSICS CHAPTER 15

3

'iitio (r#'#r to s#ctio 1.1.3).

T"# radioactiv# d#cay is a spontaneousspontaneousr#actio t"at

is unplannedunplanned* cannot be predictedcannot be predictedad

independentindependento' physical conditionsphysical conditions(suc" as

!r#ssur#* t#!#ratur#) ad chemical changeschemical changes. T"is r#actio is randomrandomr#actio +#caus# t"#

probabilityprobabilityo' a nucleus decayingnucleus decayingat a ,iv# istat

is t"# samesame'or a-- t"# uc-#i i t"# sa!-#.

Radioactiv# radiatios ar# #itt#d w"# a usta+-#uc-#us d#cays. T"# radiatios ar# alpha particles,alpha particles,

beta particles and gamma-raysbeta particles and gamma-rays.

#$.# "adioactive decay


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PHYSICS CHAPTER 15

4

A a-!"a !artic-# cosists o'two protons and two neutronstwo protons and two neutrons.

It is id#tica- to a helium nucleusa helium nucleusad its sy+o- is

It is positively chargedpositively charged!artic-# ad its va-u# is %# wit" ass

o' .//%0/3 u.

"# a uc-#us ud#r,o#s a-!"a d#cay it -os#s 'our uc-#os*

two o' w"ic" ar# !rotos* t"us t"# r#actio ca +# r#!r#s#t#d

+y ,##ra- #2uatio +#-ow:

Ea!-#s o' d#cay :

#$.#.# Alpha particle % &

He42 424R

Q++ HePbPo 4221482

21884

%'arent&%'arent& %%particle&particle&

%Daughter&%Daughter&X

A

Z +Y

4

2

A

Z + QHe4

2

Q++ HeRaTh 422268823090

Q++ HeRnRa 4222286

22688

Q++ HeThU 422349023892


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PHYSICS CHAPTER 15

5

#ta !artic-#s ar#electrons or positronselectrons or positrons(so#ti#s is ca--#d

+#ta6ius ad +#ta6!-us !artic-#s).

T"# sy+o-s r#!r#s#t t"# +#ta6ius ad +#ta6!-us (!ositro)

ar# s"ow +#-ow:

(eta-minus(eta-minus!artic-# is negatively chargednegatively chargedo' 1# ad its ass#2ua-s to t"# mass of an electronmass of an electron.

(eta-plus %positron&(eta-plus %positron&is positively chargedpositively chargedo' 1# (ati!artic-#o' #-#ctro) ad it "as t"# sa#

mass as the electronmass as the electron.

I +#ta6ius d#cay* a #-#ctro is #itt#d* t"us t"# massmass

number does not charge but the charge of the parentnumber does not charge but the charge of the parent

nucleus increasesnucleus increasesby oneby oneas s"ow +#-ow:

#$.#.) (eta particle % &

e

0

1

4R

e

0

1

+

4R

#ta6ius#ta6ius

(#-#ctro) :(#-#ctro) :

#ta6!-us#ta6!-us

(!ositro) :(!ositro) :

%'arent&%'arent& %%%Daughter&%Daughter&XAZ +Y1

AZ

+ + Qe01


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PHYSICS CHAPTER 15

6

Ea!-#s o' ius d#cay:

I +#ta6!-us d#cay* a !ositro is #itt#d* t"is ti# t"# c"ar,# o'

t"# !ar#t uc-#us d#cr#as#s +y o# as s"ow +#-ow:

7or #a!-# o'

!-us d#cay is

Q++

ePaTh 0

1

234

91

234

90

Q++ eUPa 0

123492

23491

Q++ ePoBi 0

121484

21483

%'arent&%'arent& %'ositron&%'ositron&%Daughter&%Daughter&

XAZ +Y1A

Z + Qe01

Qv +++ enp 0110

11

*eutrino*eutrinois unchargeduncharged

particle with negligibleparticle with negligible

massmass.


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PHYSICS CHAPTER 15

7

8aa rays ar# high energy photonshigh energy photons(electromagneticelectromagnetic

radiationradiation). Eissio o' ,aa ray does not change the parent nucleusdoes not change the parent nucleus

into a different nuclideinto a different nuclide* sic# #it"#r t"# c"ar,# or t"#uc-#o u+#r is c"a,#d.

A ,aa ray !"oto is #itt#d w"# a nucleus in an excitednucleus in an excited

state ma+es a transition to a ground statestate ma+es a transition to a ground state. Ea!-#s o' d#cay ar# :

It is uncharged %neutral& ray and ero massuncharged %neutral& ray and ero mass.

T"# differ between gamma-rays and x-rays of the samediffer between gamma-rays and x-rays of the same

wavelengthwavelengtho-y i t"# a#r i w"ic" they are producedthey are produced9

gamma-raysgamma-raysar# a result of nuclear processesresult of nuclear processes* w"#r#as x-x-

rays originate outside the nucleusrays originate outside the nucleus.

#$.#. amma ray % &

++ HePbPo 4221482

21884

++ eUPa 01

23492

23491

+ TiTi 2088120881

amma rayamma ray


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PHYSICS CHAPTER 15

8

Ta+-# 15.1 s"ows t"# co!ariso +#tw## t"# radioactiv#

radiatios.

#$.#./ 0omparison of the properties between alpha

particle, beta particle and gamma ray.

A-!"a #ta 8aa

C"ar,#

'-#ctio +y#-#ctric ada,#tic 'i#-ds

Ioiatio !ow#r

P##tratio !ow#r

A+i-ity to a''#ct a!"oto,ra!"ic !-at#

A+i-ity to !roduc#

'-uor#sc#c#

1)e1)e #e !" 1#e#e !" 1#e 2 %uncharged&2 %uncharged&

3es3es 3es3es *o*o

StrongStrong 4oderate4oderate 5ea+5ea+

5ea+5ea+ 4oderate4oderate StrongStrong

3es3es 3es3es 3es3es

3es3es 3es3es 3es3es6able #$.#6able #$.#


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PHYSICS CHAPTER 15

9

7i,ur#s 15.1 ad 15.% s"ow a d#'-#ctio o' * ad i#-#ctric ad a,#tic 'i#-ds.

7igure #$.#7igure #$.#

B

++++++++

E

7igure #$.)7igure #$.)

Radioactiv#

sourc#


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PHYSICS CHAPTER 15

10

;aw o' radioactiv# d#cay stat#s:

7or a radioactive source, the decay rate is directly7or a radioactive source, the decay rate is directly

proportional to the number of radioactive nucleiproportional to the number of radioactive nucleiNNremaining in the sourceremaining in the source.

i.#.

R#arra,i, t"# #2. (15.1):

H#c# t"# decay constantdecay constantis d#'i#d as the probability that athe probability that a

radioactive nucleus will decay in one secondradioactive nucleus will decay in one second. Its uit is ss##

.

#$.#.$ Decay constant % & dt

dN

Ndt

dN

Ndt

dN=

*egative sign*egative sign#as t"# number ofnumber of

remaining nuclei decreases with timeremaining nuclei decreases with time

Decay constantDecay constant

%#$.#&%#$.#&

N

dt

dN

=nucleieradioaci!re"ainin#o$nu"ber

raedeca%=


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PHYSICS CHAPTER 15

11

T"# d#cay costat is a c"aract#ristic o' t"# radioactiv# uc-#i.

R#arra,# t"# #2. (15.1)* w# ,#t

At ti# t=t=00,,N=NN=N00(initial number of radioactive nucleiinitial number of radioactive nucleii t"#

sa!-#) ad a't#r a timetime tt* t"# number of remaining nucleinumber of remaining nucleiis

NN. It#,ratio o' t"# #2. (15.%) 'ro t=0to ti# t:

dtN

dN = %#$.)&%#$.)&

=tN

N

dtN

dN

00

[ ] [ ]tNN

tN 00ln =

tN

N =0

ln

teNN

= 0Exponential law ofExponential law of

radioactive decayradioactive decay%#$.&%#$.&


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PHYSICS CHAPTER 15

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7ro t"# #2. (15.3)* t"us t"# ,ra!" o'N* t"# u+#r o'

r#aii, radioactiv# uc-#i i a sa!-#* a,aist t"# ti# tis

s"ow i 7i,ur# 15.3.

teNN

= 0

2

0N

0N

4

0N

16

0N8

0N

2/1T 2/12T 2/13T 2/14T 2/1&T0t'i"e

N

li$ehal$(2/1 T

7igure #$.7igure #$.

Stiu-atio 15.1

*ote:*ote:

7ro t"# ,ra!" (d#cay curv#)*t"# life of any radioactivelife of any radioactive

nuclide is infinitynuclide is infinity* t"#r#'or# to

ta-k a+out t"# -i'# o' radioactiv#

uc-id#* w# r#'#r to its half-lifehalf-life.
http://opt/scribd/conversion/tmp/scratch2504/G:/P&P/Semester1/Latest/p11_01_01_01a.swfhttp://opt/scribd/conversion/tmp/scratch2504/G:/P&P/Semester1/Latest/p11_01_01_01a.swfhttp://af_4409.html/


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PHYSICS CHAPTER 15

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is d#'i#d as the time ta+en for a sample of radioactivethe time ta+en for a sample of radioactive

nuclides disintegrate to half of thenuclides disintegrate to half of the initial number of nucleiinitial number of nuclei. 7ro t"# #2. (15.3)* ad t"# d#'iitio o' "a-'6-i'#*

w"# * t"us

T"# half-life of any given radioactive nuclidehalf-life of any given radioactive nuclideis constantconstant* it

does not depend on the number of remaining nucleidoes not depend on the number of remaining nuclei.

#$.#.8 9alf-life %T1/2

&

teNN = 0

2/1Tt=2

) 0N

N=

2/1

00

2TeNN =

2/12 Te=

2/1

21 Te =

2/1ln2ln Te=

T 693*02ln2/1 ==9alf-life9alf-life %#$./&%#$./&


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PHYSICS CHAPTER 15

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T"# uits o' t"# "a-'6-i'# ar# secondsecond(s)* minuteminute(i)* hourhour

("r)* dayday (d) ad yearyear(y). Its unit depend on the unit of decayunit depend on the unit of decay

constantconstant. Ta+-# 15.% s"ows t"# va-u# o' "a-'6-i'# 'or s#v#ra- isoto!#s.

6able #$.)6able #$.)

sotope 9alf-life

.5 1/


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PHYSICS CHAPTER 15

15

+econdperdeca%+10,3-i1 10

. =

is d#'i#d as the decay rate of a radioactive sample.the decay rate of a radioactive sample.

Its uit is number of decays per secondnumber of decays per second.

4t"#r uits 'or activity ar# curiecurie (0i0i) ad bec;uerelbec;uerel((;(;) > S.I.

uit.

?it cov#rsio:

R#-atio +#tw## activity (A) o' radioactiv# sa!-# ad ti# t:

7ro t"# -aw o' radioactiv# d#cay :

ad d#'iitio o' activity :

#$.#.< Activity of radioactive sample %A&

dt

dN

+econdperdeca%1B.1 =

Ndt

dN=

dt

dNA =


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PHYSICS CHAPTER 15

16

T"us

00 NA =

NA = ad teNN = 0( )teNA = 0

teAA = 0

Activity at timeActivity at time tt Activity at time,Activity at time,

tt=2=2

ad( ) teN = 0

%#$.$&%#$.$&


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PHYSICS CHAPTER 15

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A radioactiv# uc-id# A disit#,rat#s ito a sta+-# uc-id# . T"#

"a-'6-i'# o' A is 5./ days. I' t"# iitia- u+#r o' uc-id# A is1./ 1/%/* ca-cu-at# t"# u+#r o' uc-id# a't#r %/ days.

Solution :Solution :

T"# d#cay costat is ,iv# +y

T"# u+#r o' r#aii, uc-id# A is

T"# u+#r o' uc-id# A t"at "av# d#cay#d is

T"#r#'or# t"# u+#r o' uc-id# 'or#d is

Ea!-# 1 :

QBA +

0*&2ln=

da%+20)101*0da%+)0*& 2002/1 === tNT

2/1

2ln

T=

1da%+139*0 =

t

eNN

= 0 ( ) ( ) ( )20139*020

100*1

= eN nuclei102*6 18=1820 102*6100*1 =

nuclei1038*9 19=

nuclei1038*9

19


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PHYSICS CHAPTER 15

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a. Radioactiv# d#cay is a rado ad s!ota#ous uc-#arr#actio. E!-ai t"# t#rs rado ad s!ota#ous.

+. =/@ o' a radioactiv# su+stac# d#cays i ./ days. t#ri#

i. t"# d#cay costat*

ii. t"# "a-'6-i'# o' t"# su+stac#.


a. Rado #as t"at t"# time of decay for each nucleustime of decay for each nucleus

cannot be predictedcannot be predicted. T"# probability of decay for eachprobability of decay for each

nucleus is the samenucleus is the same.

S!ota#ous #as it happen by itself without externalhappen by itself without external

stimulistimuli. T"# decay is not affected by the physical conditionsdecay is not affected by the physical conditions

and chemical changesand chemical changes.

Ea!-# % :


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PHYSICS CHAPTER 15

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+. At ti#

T"# u+#r o' r#aii, uc-#i is

i. y a!!-yi, t"# #!o#tia- -aw o' radioactiv# d#cay* t"us t"#

d#cay costat is

ii. T"# "a-'6-i'# o' t"# su+stac# is

da%+'0*4=t

= 0010080 NNN

nuclei2*0 0N=

teNN = 0 ( )0*4002*0 = eNN( )0*42*0 =e

( )0*4ln2*0ln = e

1da%402*0 =( ) eln0*42*0ln

=

2ln2/1 =T

402*0

2ln2/1 =T

da%+,2*12/1 =T


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PHYSICS CHAPTER 15

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P"os!"orus63% is a +#ta #itt#r wit" a d#cay costat o' 5.0 1/

s1. 7or a !articu-ar a!!-icatio* t"# !"os!"orus63% #its ./ 1/

+#ta !artic-#s #v#ry s#cod. t#ri#

a. t"# "a-'6-i'# o' t"# !"os!"orus63%*

+. t"# ass o' !ur# !"os!"orus63% wi-- ,iv# t"is d#cay rat#.

(8iv# t"# Avo,adro costat* BA0./% 1/%3o-1)


a. T"# "a-'6-i'# o' t"# !"os!"orus63% is ,iv# +y

Ea!-# 3 :

2ln2/1 =T

1,1, +104*0)+106*& ==dt

dN

,106*&

2ln

=

+1024*1

6

2/1 =T


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PHYSICS CHAPTER 15

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+. y usi, t"# radioactiv# d#cay -aw* t"us

0./% 1/%3uc-#i o' P63% "as a ass o' 3% ,

.1 1/13uc-#i o' P63% "as a ass o'

1,1, +104*0)+106*& ==dt

dN

0Ndt

dN=

( ) 0,, 106*&100*4 N=nuclei1014*, 130 =N

32

1002*6

1014*,23

13

#1080*3 9=


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PHYSICS CHAPTER 15

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A t"oriu6%%= isoto!# w"ic" "as a "a-'6-i'# o' 1.


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PHYSICS CHAPTER 15

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+. y usi, t"# uit cov#rsio ( -ideca%/+econd )*

t"# activity is

Sic# t"#

I' 0./% 1/%3uc-#i o' T"6%%= "as a ass o' %%= , t"us

3.=0 1/1


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PHYSICS CHAPTER 15

24


c. I' %%= , o' T"6%%= cotais o' 0./% 1/%3uc-#i t"us

15./ , o' T"6%%= cotais o'

T"#r#'or# t"# u+#r o' #itt#d a-!"a !artic-#s !#r s#cod is

,iv# +y

( )231002*6228

0*1&

nuclei1096*3 22=N

( ) 228 1096*3101&*1 = N

dt

dNA ==

+econdparicle+/10&&*4 14 = A

I,or#d it.


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PHYSICS CHAPTER 15

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At the end of this chapter, students should be able to:At the end of this chapter, students should be able to:

ExplainExplainthe application of radioisotopes as tracers.the application of radioisotopes as tracers.

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15.% Radioisoto!# as trac#rs (1"our)


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PHYSICS CHAPTER 15

26

#$.).# "adioisotope is d#'i#d as an isotope of an element that is radioactivean isotope of an element that is radioactive. It is !roduc#d i a uc-#ar r#actor* w"#r# stable nuclei arestable nuclei are

bombarded by high speed neutrons until they becomebombarded by high speed neutrons until they become

radioactive nucleiradioactive nuclei.

Ea!-#s o' radioisoto!#s:

a.

+.

c.

#$.) "adioisotope as tracers

Q+++ PnP 321&10311&

Q++ eP 0

1

32

16

32

1&

Q+++ ana 24111

0

23

11

Q++ e#a 0

1

24

12

24

11

Q+++ lnl 28131

0

2,

13

Q++ eil 0128142813

%"adio phosphorus&%"adio phosphorus&

%"adio sodium&%"adio sodium&

%"adio aluminum&%"adio aluminum&


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PHYSICS CHAPTER 15

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Sic# radioisotoperadioisotope"as t"# same chemical properties as thesame chemical properties as the

stable isotopesstable isotopest"# t"#y ca +# us#d to trace the path madetrace the path madeby the stable isotopesby the stable isotopes.

Its #t"od :

A small amount of suitable radioisotopesmall amount of suitable radioisotopeis #it"#r

swallowedswallowed+y t"# !ati#t or in>ected into the body of thein>ected into the body of the

patientpatient. A't#r a w"i-# c#rtai !art o' t"# +ody wi-- "av# a+sor+#d

#it"#r a ora- aout* or a aout w"ic" is -ar,#r t"a

ora- or -#ss t"a ora- o' t"# radioisoto!#. A detectordetector

(suc" as eiger counter ,gamma cameraeiger counter ,gamma camera* #tc..) t"#

measures the count rate at the part of the bodymeasures the count rate at the part of the bodyconcernedconcerned.

It is us#d to investigate organsinvestigate organs i "ua +ody suc" as kid#y*

t"yroid ,-ad* "#art* +rai* ad #tc..

It a-so us#d to monitor the blood flowmonitor the blood flowad measure the bloodmeasure the blood

volumevolume.

#$.).) "adioisotope as tracers


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PHYSICS CHAPTER 15

28

A sa-- vo-u# o' a so-utio w"ic" cotai#d a radioactiv# isoto!#

o' sodiu "ad a activity o' 1%/// disit#,ratios !#r iut# w"#it was iD#ct#d ito t"# +-oodstr#a o' a !ati#t. A't#r 3/ "ours t"#

activity o' 1./ c3o' t"# +-ood was 'oud to +# /.5/ disit#,ratios

!#r iut#. I' t"# "a-'6-i'# o' t"# sodiu isoto!# is tak# as 15

"ours* #stiat# t"# vo-u# o' +-ood i t"# !ati#t.

Solution :Solution :T"# d#cay costat o' t"# sodiu isoto!# is

T"# activity o' sodiu a't#r 3/ " is ,iv# +y

Ea!-# 5 :

h30)"in12000h)1& 1

02/1 ===

tAT

2ln2/1 =T

2ln1& =

12 h1062*4 =

teAA = 0( ) ( )( )301062*4

2

12000= e

1

"in3000

=A


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PHYSICS CHAPTER 15

29


I t"# dilutiondilutiontraci, #t"od* t"# activityactivityo' t"# sa!-#*AAis

proportionalproportionalto t"# volumevolumeo' t"# sa!-# !r#s#t* VV.

t"us t"# ratio o' activiti#s is ,iv# +y

T"#r#'or# t"# vo-u# o' t"# +-ood is

h30)"in12000h)1& 102/1 === tAT

VA11 kVA = 22 kVA =t"# ad

2

1

2

1

V

V

A

A=

2

1

3000

&*0

V=

32 c"6000=V

initialinitial finalfinal

%#$.8&%#$.8&


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PHYSICS CHAPTER 15

30

n medicinen medicine To d#stroy cac#r c#--s +y ,aa6ray 'ro a "i,"6activity

sourc# o' Co60/.

To tr#at d##!6-yi, tuors +y !-ati, radiu6%%0 or ca#siu6

13 isid# t"# +ody c-os# to t"# tuor.

n agriculturen agriculture

To #a+-# sci#tists to 'oru-at# '#rti-i#rs t"at wi-- icr#as# t"#

!roductio o' 'ood.

To d#v#-o! #w strais o' 'ood cro!s t"at ar# r#sistat to

dis#as#s* ,iv# "i," yi#-d ad ar# o' "i," 2ua-ity. To icr#as# t"# ti# 'or 'ood !r#s#rvatio.

#$.). !ther uses of radioisotope


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PHYSICS CHAPTER 15

31

n industryn industry

To #asur# t"# w#ar ad t#ar o' ac"i# !art ad t"#

#''#ctiv##ss o' -u+ricats.

To d#t#ct '-aws i ud#r,roud !i!#s #.,. !i!#s us# to carry

atura- !#tro-#u ,as.

To oitor t"# t"ick#ss o' #ta- s"##t duri, au'actur# +y

!assi, it +#tw## ,aa6ray ad a suita+-# d#t#ctor.n archaeology and geologyn archaeology and geology

To #stiat# t"# a,# o' a arc"a#o-o,ica- o+D#ct 'oud +y

r#'#rri, to car+o61 dati,.

To #stiat# t"# ,#o-o,ica- a,# o' a rock +y r#'#rri, to

!otassiu6/ dati,.


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PHYSICS CHAPTER 15

32

Radioactiv# iodi# isoto!# o' "a-'6-i'# =./ days is us#d 'ort"# tr#at#t o' t"yroid ,-ad cac#r. A c#rtai sa!-# is r#2uir#d to

"av# a activity o' =./ 1/52 at t"# ti# it is iD#ct#d ito t"# !ati#t.

a. Ca-cu-at# t"# ass o' t"# iodi#6131 !r#s#t i t"# sa!-# to

!roduc# t"# r#2uir#d activity.

+. I' it tak#s % "ours to d#-iv#r t"# sa!-# to t"# "os!ita-* w"at

s"ou-d +# t"# iitia- ass o' t"# sa!-#

c. "at is t"# activity o' t"# sa!-# a't#r % "ours i t"# +ody o' t"#

!ati#t

(8iv# t"# Avo,adro costat* BA0./% 1/%3 o-1)

Ea!-# 0 :

( )131

&3


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PHYSICS CHAPTER 15

33


T"# d#cay costat o' t"# iodi# isoto!# is

a. 7ro t"# r#-atio +#tw## t"# d#cay rat# ad activity*

I' 0./% 1/%3 uc-#i o' 6131 "as a ass o' 131 , t"us

=./ 1/11 uc-#i o' 6131 "as a ass o'

( ) +)1091*66060240*8 &2/1 ==TB.100*8 &0 =A

2ln2/1 =T

2ln1091*6 & =

16 +1000*1 =

0

0

=dt

dNA

( ) 0

6& 1000*1100*8 N=00 NA =

nuclei100*8 110 =N

1311002*6

100*823

11

#10,4*1 10=


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PHYSICS CHAPTER 15

34


+. 8iv#

;#tN: ass o' 6131 a't#r % "ours

N0: iitia- ass o' 6131

y a!!-yi, t"# #!o#tia- -aw o' radioactiv# d#cay* t"us

c. 8iv#

T"# activity o' t"# sa!-# is

( ) +)1091*66060240*8 &2/1 ==TB.100*8 &0 =A

+108*64360024hr24 4===t#10,4*1 10=

t

eNN

= 0 ( )( )46 1064*81000*10

1010,4*1

= eN( ) ( )( )

46 1064*81000*110

0 10,4*1 = eN

#1090*1 10

0

=N+108*64360024hr24 4===t

teAA

= 0 ( ) ( )( )46 1064*81000*1&

100*8 = eA

B.1034*, &

=A


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PHYSICS CHAPTER 15

35

A arc"#o-o,ist o a di, 'ids a 'ra,#t o' a aci#t +ask#t

wov# 'ro ,rass. ;at#r* it is d#t#ri#d t"at t"# car+o61cot#t o' t"# ,rass i t"# +ask#t is


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PHYSICS CHAPTER 15

36

E#rcis# 15.1 :8iv#N0./% 1/

%3 o-1

1. ;ivi, wood tak#s i radioactiv# car+o61 'ro t"#atos!"#r# duri, t"# !roc#ss o' !"otosyt"#sis* t"# ratio o'car+o61 to car+o61% atos +#i, 1.%5 to 1/1% . "# t"#wood di#s t"# car+o61 d#cays* its "a-'6-i'# +#i, 50// y#ars. , o' car+o 'ro a !i#c# o' d#ad wood ,av# a tota- cout rat#o' %/./ disit#,ratios !#r iut#. t#ri# t"# a,# o' t"#

!i#c# o' wood.

A*S. :A*S. : ?


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PHYSICS CHAPTER 15

Good luck

7or

%d s##st#r #aiatio

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