1.	(a)	decrease	1
for 1 mark
(b)	(i)	none would go through paper	1
for 1 mark
(ii)	all would go through paper	1
for 1 mark
(iii)	only some absorbed/amount absorbed	2
depends on thickness of paper 
for 1 mark each

2.	(a)	(i)	beta and gamma  (any order) 	1
for one mark
(ii)	gamma	1
for one mark
(b)	(i)	particles / atoms / molecules become charged / gain / lose 	1
electrons
for one mark
(ii)	e.g. to kill cancer cells  (allow any use of alpha, beta or gamma
or X- radiation) 	1
for one mark
(c)	(i)	time taken for no. of atoms / no. of nuclei / mass of U238 /	1
activity to halve – not radioactivity
or
time taken for count rate to halve
for one mark
(ii)	atoms with unstable nuclei	2
which emit radiation
(not definition of isotope but isotope which is radioactive gets 1 mark)
for 1 mark each
(d)	(i)	1 / 4     accept 25% or 0.25	1
for one mark

(ii)	2 × half life  or  2 × 4500  million years (independent of (i)) 	2
gains 1 mark
but
9000 million years   ecf only if answer to (i) is , etc.
gains 2 marks
[10]

3.	(a)	(i)	helium nuclei	1
or
two protons and two neutrons or  He
do not accept it is a particle emitted by an unstable nucleus of Californium -241
(ii)	time taken for the activity or count rate or number of nuclei	1
or number of atoms or number of radioactive particles
to decrease to half

(iii)	Technetium-99	1
this mark cannot score without Technetium- 99
	any two of the following:	2
•	suitable short half-life or activity quickly reduced to
a safe level or it doesn’t stay in the body long
this mark can score if Cobalt -60 is given
•	(gamma emitter so) it can be detected outside the body
less (ionising) damage to cells or tissue
this mark can score if Cobalt -60 is given
(b)	any three of the following:	3
•	transport of waste into the area
•	possibility of accident or leakage from transport
•	safe levels not reached for hundreds or thousands of years
Possible leakage or contamination of land or water or increase in background radiation
increased risk of (radiation linked) illness or cancer

4.	(a)	(i)	nucleus / neutron	1
do not accept shells or orbits
(ii)	-1	1