Measuring decay

Question 1

The instability of a nucleus can be caused by

Answer 1

having too many neutrons
not enough neutrons
too much energy

Question 2

The nucleus decays by

Answer 2

releasing energy/particles until it reaches a stable form

Question 3

Alpha particles from a given isotope are always emitted with _____ kinetic energy because

Answer 3

equal

they move apart with equal and opposite amounts of momentum

Question 4

Beta particles emit neutrinos or antineutrinos and so the energy released is

Answer 4

shared in variable proportions

Question 5

How can the radioactive nature of a source be determined

Answer 5

using absorption tests where a Geiger tube is used to measure the count rate of a source penetrating through different materials.

Question 6

Alpha particle tracks in a cloud chamber

Answer 6

straight trains that radiate from the source and are easily visible. They are all the same length indicating that alpha particles have the same range.

Question 7

Why are tracks left in the cloud chamber

Answer 7

due to the ionisation of the air saturated with vapour in the cloud chamber, an alpha or beta particle passing through the cloud chamber leaves a visible track of condensed vapour droplets

Question 8

Beta particle tracks in a cloud chamber

Answer 8

Wispy tracks that area easily deflected as a result of collisions with air molecules. The tracks aren’t as easy to see compared to alpha particles because beta particles are less ionising

Question 9

Count rate =

Answer 9

the number of counts per second

Question 10

Background radiation occurs naturally due to

Answer 10

cosmic radiation

radioactive materials in rocks and the air

Question 11

Before a source is tested, what needs to be measured

Answer 11

the count rate due to the background radioactivity - the count rate is measured without the source to measure the background activity which can be subtracted from the measured count rates to give the correct value.

Question 12

Absorption tests:

Answer 12

• measure background activity and subtract

- use absorbers of different thickness of the same material so the effect of the absorber thickness can be investigated

Question 13

Man made background radiation examples

Answer 13

nuclear weapons

nuclear waste

Question 14

Radioactive decay is completely random because

Answer 14

any sample of an isotope has the same rate of decay

Question 15

Subtract _______ from the source reading

Answer 15

background radiation