ch29 - nuclear physics

Question 1

nucleus before decay

Answer 1

parent nucleus

Question 2

nucleus after decay

Answer 2

daughter nucleus

Question 3

in alpha decay

Answer 3

. nucleon number decreases by 4
. proton number decreases by 2

Question 4

in beta - decay

Answer 4

. nucleon number doesnt change
. proton number increases by 1

Question 5

in beta + decay

Answer 5

. nucleon number us unchanged
. proton number decreases by 1

Question 6

in gamma decay

Answer 6

. nucleon number unchanged
. proton number unchanged

Question 7

in a stable nucleus

Answer 7

nucleons are tightly bound by a strong nuclear force

Question 8

do seperate nucleons have more or less mass than the nucleus

Answer 8

MORE

Question 9

to dismantle a nucleus

Answer 9

work done against strong nuclear force

Question 10

why does seperated nucleons have more mass

Answer 10

. work done against nuclear force to seperate nucleons
. each nucleon in deep potential well
. each nucleon has more potential energy
. this energy transferred to mass

Question 11

einstein’s mass energy equation

Answer 11

<>E = <>mc²
E = c²<>m
E = mc²

Question 12

accordingto einstein’s equation

Answer 12

. mass of system increases when energy is SUPPLIED
. mass of system decreases when energy is RELEASED

Question 13

proton rest mass

Answer 13

1.672 623 * 10 ^-27

Question 14

neutron rest mass

Answer 14

1.674 929 * 10 ^-27

Question 15

12, 6 C nucleus rest mass

Answer 15

19. 926 483 * 10 ^-27

Question 16

mass defect

Answer 16

the difference between the total mass of the individual seperate nucleons and the mass of the nucleus

Question 17

E = mc² applies to all energy changes

Answer 17

. includes chemical reactions
. not just nuclear processes

Question 18

atomic mass unit

Answer 18

1/12 of the mass of a neutral atom or carbon-12

Question 19

u to kg

Answer 19

1.66 * 10^ - 27

Question 20

if negative change in mass

Answer 20

energy is lost

Question 21

binding energy

Answer 21

the minimum external energy required to completely seperate all the neutrons and protons of a nucleus to infinity

Question 22

binding energy is EXTERNAL, NOT stored in nucleus

Question 23

findinf binding energy per nucleon

Answer 23

. determine mass defect for nucleus
. use E = mc² for binding energy of nucleus
. divide the nucleus binding energy by number of nucleons

Question 24

higher bindig energy

Answer 24

more stable

Question 25

nucleus with highest binding energy / most stable isotope in nature

Answer 25

56, 26 Fe

Question 26

stable nuclei

Answer 26

. 12, 6 C . 16, 8 O . 4, 2 He

Question 27

for nuclides with A > 20

Answer 27

. not much variation in binding energy per nucleon

Question 28

fission

Answer 28

the process in which a massive nucleus

Question 29

induced fission

Answer 29

. split nucleus by firing a slow moving neutron at it

Question 30

induced fission reaction

Answer 30

1,0 neutron + 235, 92 U => 236, 92 U => 142, 56 Ba + 92, 36 Kr + 2 1,0 neutron

Question 31

uranium - 236

Answer 31

highly unstable

Question 32

in the induced fission uranium reaction

Answer 32

. energy released . two fast moving electrons released . two product fragments have more binding energy

Question 33

fusion

Answer 33

the process in which two light nuclei join together to form a heavier nucleus

Question 34

which fusion reaction takes place in the core of many stars

Answer 34

2,1 H + 1,1 proton => 3, 2 He

Question 35

Geiger Muller (GM) tube

Answer 35

. detects radiation from weak source . each count is reresents detection of alpha/beta particle of gamma ray photon . counter beeps in random, irregular manner

Question 36

ratemeter

Answer 36

. measures faster rates of radiation . fluctuating needle . has control for setting the time constant . fluctuations more smooth on 5s setting

Question 37

spontaneous decaying

Answer 37

. radioactive decay occurs for unstable nucleus . cannot be predicted

Question 38

for radioactive substance, number of undecayed nuclei

Answer 38

gradually decreases

Question 39

radioactive decay is

Answer 39

. spontaneous . random

Question 40

radioactive decay is spontaneous

Answer 40

. decay of particular nucleus is not affected by other nuclei . not affected by chemical reactions or external factors like temperature and pressure

Question 41

radioactive decay is random

Answer 41

. can't predict when a particluar nucleus will decay . each nucleus has same chance of decaying per unit time

Question 42

decay constant, lambda

Answer 42

the probability that an individual nucleus will decay per unit time interval units = s-1, min -1, h -1, y -1

Question 43

activity, A

Answer 43

the rate of decay of nuclei of a radioactive source unit = becquerel, Bq

Question 44

formula for activity

Answer 44

A = - rate constant * N minus sign means number of decayed nuclei decreases with time

Question 45

more the decay constant

Answer 45

greater the activity of sample

Question 46

count rate, R

Answer 46

the number of particles or gamma photons detected per unit time by a GM tube always a fraction of the activity of a sample

Question 47

corrected count rate

Answer 47

count rate - background radiation

Question 48

exponential decay

Answer 48

the decrease of a quanitiy where the rate of decrease is proportional to the value of the quantity

Question 49

half life

Answer 49

the half life of an isotope is the mean time taken for half of the active nuclei in a sample to decay

Question 50

equations for radioactive decay

Answer 50

N = No e^-lambda*t A = Ao e^-lambda*t R = Ro e^-lambda*t X = Xo e^-lambda*t Xo is that at time = 0

Question 51

relating decay constant and half life

Answer 51

lambda = ln2/ (t1/2) lambda = 0.693/ half life

Question 52

lambda = ln2/ (t1/2) equation derivation

Answer 52

x = ln y N = No * e^ -lambda* t N/No = e^ (-lambda* t1/2) = 1/2 e^ (lambda* t1/2) = 2 lambda* t1/2 = ln2 lambda = ln2/ (t1/2)