3.8 Nuclear Physics

Question 1

activity

Answer 1

A - the number of nuclei of a radioactive isotope

Question 2

Unit of activity?

Answer 2

Bq

Question 3

background radiation

Answer 3

radiation due to naturally occurring radioactive substances in the environment that is continuous: buildings, cosmic radiation, argon in air

Question 4

binding energy of a nucleus

Answer 4

work that must be done to separate a nucleus into its constituent neutrons and protons = mass defect x c^2

Question 5

binding energy per nucleon

Answer 5

average work that must be done - to separate a nucleus into its constituent nucleons - per nucleon

Question 6

count rate

Answer 6

number of counts per unit time - measured using Geiger Muller tube

Question 7

critical mass

Answer 7

minimum mass of fissile isotope in a nuclear reactor necessary to produce the chain reaction - if less than critical mass the chain reaction won’t occur as too many neutrons escape from fission reactor or absorbed without fission

Question 8

decay consant

Answer 8

probability of an individual nucleus decaying per second

Question 9

what can be used to determine the diameter of the nucleus of a substances atoms?

Answer 9

high energy electron scattering

Question 10

units of radiation

Answer 10

Sv - Sievert

Question 11

fission

Answer 11

splitting of a large unstable nuclei into 2 smaller, more stable nuclei that are approximately equal in size

Question 12

induced fission

Answer 12

fission that occurs when the large, unstable nuclei collides with an incoming neutron

Question 13

fusion

Answer 13

fusing together of 2 smaller, unstable nuclei to form a larger, more stable one

Question 14

thermal fusion

Answer 14

fusing together of metals by melting them

Question 15

half life

Answer 15

time taken for the mass of a radioactive isotope to decrease to half the initial value - could also be the activity of the sample or the number of nuclei of the sample

Question 16

impulse

Answer 16

force multiplied by the time for which the force acts

Question 17

intensity of radiation

Answer 17

radiation energy per second per unit area at normal incidence to the surface

Question 18

ionising radiation

Answer 18

radiation that produces ions in the substances it passes through - destroys cell membranes and damages vital molecules like DNA by creating ‘free radical ions’ which react with the DNA

Question 19

inverse square law for gamma radiation

Answer 19

intensity of gamma radiation from a point source varies with the inverse of the square of the distance from the source

Question 20

Rutherford’s alpha particle scattering experiment

Answer 20

• Demonstrated that every atom contains a positively charged nucleus much smaller than the atom
• This is where all the positive charge and where most of the mass is

Question 21

thermal nuclear reactor

Answer 21

nuclear reactor which has a moderator at the centre