Radioactivity

Question 1

what did rutherford’s scattering experiment prove?

Answer 1

the exsistence of the nucleus

Question 2

what three things were observed during the alpha scattering experiment

Answer 2

most alpha particles passed straight through the foil with no deflection
small amount of particles deflected by a large angle
very few particles were defelected back by more than 90°

Question 3

describe the plum pudding model

Answer 3

atoms made up of a sphere of positive charge

small areas of negative charge evenly distributed throughout

Question 4

what are the three types of radiation

Answer 4

Alpha
Beta
Gamma

Question 5

what are the properties of alpha radiation

Answer 5

range of 2-10cm in air
highly ionising
deflected by magnetic and electric fields
absorbed by paper

Question 6

what are the properties of beta radiation

Answer 6

range of 1m in air
weakly ionising
deflected by electric and magnetic fields
absorbed by aluminium foil

Question 7

what are the properties of gamma radiation

Answer 7

infinite range in air follows inverse square law
very weakly ionising
not deflected by electric and magnetic fields
absorbed by a few Km of concrete or few inches of lead

Question 8

outline an experiment that can be used to detect the three different types of radiation

Answer 8

Using a Geiger-miller tube find the background count when the source is not present
place the source of radiation close to GM tube and measure the count rate
place a sheet of paper if count rate reduces source is emitting alpha radiation repeat with aluminium foil and lead

Question 9

name three uses of gamma radiation in medicine

Answer 9

As a detector
sterilising medical equipment
in radiation therapy

Question 10

outline how gamma radiation can be used as a detector

Answer 10

radioactive source with a short half life which emits gamma radiation can be injected into a patient
and the gamma radiation can be detected using gamma cameras in order to help diagnose patients

Question 11

outline how gamma radiation can be used to sterelise medical equipment

Answer 11

gamma radiation will kill any bacteria present on the equipment

Question 12

outline how gamma radiation can be used in radiation therapy

Answer 12

gamma radiation can be used to kill cancerous cells in a targeted region of a body such as a tumour however it will also kill all healthy cells in that region

Question 13

what does gamma radiation do in air as it travels and why does this occur

Answer 13

it spreads out in all directions equally

therefore it obeys an inverse square law

Question 14

what is half life

Answer 14

the time taken for the mass of a radioactive isotope to decrease to half the intial mass or activity

Question 15

name four sources of background radiation

Answer 15

radon gas
rocks
cosmic rays
artificial sources

Question 16

what is the decay constant

Answer 16

the probability of an individual nucleus decaying per second

Question 17

what is the activity of a radioactive isotope

Answer 17

the number of nuclei of the isotope that disintegrate per second

Question 18

why is ionising radiation hazardous

Answer 18

as it can damage living cells

Question 19

how can ionising radiation affect living cells

Answer 19

it can destroy cell membranes

it can damage vital molecules such as DNA by forming free radical ions which react with vital molecules

Question 20

name 6 examples of ionising radiation

Answer 20

gamma 
alpha 
beta 
neutrons 
protons 
x-rays

Question 21

what does gamma radiation consist of

Answer 21

photons

Question 22

what is intensity of radiation

Answer 22

the radiation energy per second passing normally through unit area

Question 23

why does a beam of high energy electrons get diffracted by a target nuclei

Answer 23

as the de broglie wavelength of the electrons is similar to the diameter of the target nucleus