Radiation Flashcards
Explain why this γ-emission does not affect the numbers in the equation.
has no charge
Suggest one reason why a nucleus of thallium-208 is unstable.
excess neutrons
How to calculate neutrons.
Top-Bottom=Neutrons
How to calculate electrons.
Same as protons in a neutral atom
From the data given for positions A, B and C, deduce the type of emissions coming from the radioactive source. Explain your reasoning.
B- gamma, not deflected, not charged
C- beta, charged particles deflected (L rule)
A- background detected here
State the nature of γ-rays
electromagnetic radiation of high frequency and short wavelength
Compare the deflections of the paths of the two types of particle.
deflect in opp directions
β deflected more
Describe the path of the beta particles.
curved path
deflected towards positively charged plate
State the nature of an α-particle.
2 protons, 2 neutrons
Describe how an electric field between two charged plates could be used to determine whether a beam of particles consists of α- or β-particles.
α towards negative (plate)
β towards positive (plate)
State what is meant by the term isotopes
Different version of the same element.
Same number of protons.
Different number of neutrons (,,a diff nucleon number)
State and explain the type of radiation that must be emitted by the isotope for the leak to be detected.
Gamma, can penetrate through the surface and ground and reach the detector unlike the other radiation which are stopped before that
The half-life of the isotope used is 6.0 hours.
Explain why an isotope with this half-life is suitable for a crack in a water pipe.
long enough to find leak
short enough to disappear quickly
What is alpha stopped by?
thin sheet of paper
What is beta stopped by?
thin sheet of aluminium
What is gamma stopped by?
thick lead or concrete
What is the alpha charge?
+ 3.2 × 10–19
What is the beta charge?
-1.6 x 10 -19
The radiation is said to be ionising. Explain what this means
atoms lose electrons
α-particles are more strongly ionising and have a shorter range in air than γ-rays.
Use your knowledge of the nature of these radiations to explain these differences.
(2 points)
α travels more slowly, loses energy with each collision so range is short
α is charged, somore ionising because it has greater charge
At first, the detector continues to register a low count rate sometimes slightly less than the count rate registered without the source.
The count rate suddenly increases to a very high value when the source is very close to the detector.
Explain these changes in the count rate.
Low count rate due to background.
Slightly less due to random decaying fashion.
High due to emission from source.
He notices that the count rate registered by the detector every year is slightly smaller than it was the previous year.
Suggest why this is so.
Decay of source slowed down =
Activity decreased due to less radioctive nuclei
A lead sheet of thickness 10 mm is positioned between the detector and the radioactive source.
State and explain what happens to the count rate on the detector.
decreases, not completely absorbed
Suggest why the paths of the particles in the magnetic field are curved.
the force on the particles is perpendicular to their paths
Describe the results from this scattering experiment and explain what they show about the structure of atoms.
straight->mostly empty space,
nucleus tiny
small number deflected through large angles-> most mass in nucleus, nucleus is
positive
An atom of a different element has a nucleon number of 241.
State two differences between the composition of a nucleus of this atom and a nucleus of americium-241
number of protons and neutrons
Explain why α-particles are more strongly ionising than β-particles
more ke, more charge
explain the advantage of this long half-life for the use and safe disposal of a household smoke alarm.
low activity, so not hazardous to humans, disposal of old detectors is easy and cheap
Household smoke alarm:
type of radioactive emission-
explanation-
Half-life-
alpha, highly ionising, 100 years
measuring the thickness of aluminium strips produced in a factory
type of radioactive emission-
explanation-
half-life-
beta
absorption depends on thickness of aluminium
any number of years
State two different sources of background radiation.
radon gas (in the air)
rocks OR buildings
food OR drink
cosmic rays
Suggest why isotope X2 is stable whereas X1 is not stable.
(X2) has fewer (excess) neutrons
Suggest one reason why isotopes with very short half-lives are especially hazardous.
high dose (of radiation) in short time
Deuterium is an isotope of hydrogen (H) with 1 proton and 1 neutron. Nuclear fusion occurs
when two nuclei of deuterium combine. An isotope of helium (He) and a neutron are formed.
2
1H
+
2
1H
→
3
2He
+
1
0 n
Nuclide equation for fusion.
combine, make note of any particles formed
During β-decay, one of the neutrons in the nucleus changes. Explain how charge is conserved during this change.
charge on neutron = 0 OR total charge on products = 0
charge on proton = +1 AND charge on electron =
–1
Describe the composition and structure of a neutral atom of uranium‐235.
Very small nucleus surrounded by electrons in the orbit. This many protons=the same number of electrons. This many neutrons.
Nuclear fission nuclide equation.
Minusing, make note of any particles formed
State the proton number, nucleon number, electron number and the value of the charge on an beta-particle.
0 protons, o nucleons, 1 electron, -1
How to remember the speeds of the different ionising radiation
She believes we (community) remember sun brighten
Beta decay?
plus one proton, one fewer neutron
0
-1 β
Alpha decay?
minus 2 protons and 4 nucleons
4
2 α.
Describe how the americium-241 ionises air
alpha emitted hits air molecules and remove electrons from molecules
Explain why an extremely high temperature is needed when forcing these two nuclei together.
same charge, repels, high quantity of energy to do so…
β-particles ionise the air they pass through less strongly than the same number of αparticles. Suggest why this is so.
smaller charge
travel faster (unlikely to hit)
force on electrons is less
Suggest reasons for using an α‐particle emitter in a smoke detector
highly ionizing, ionize air more easily
short range in air, stopped by smoke
do not travel out and cause harm (safe because short range)
Explain why the radioactive isotope does not have a very short half-life.
(very short half-life) doesn’t allow time for detection before activity has dropped to too low a level
Explain why the radioactive isotope does have a very long half-life.
(very long half-life) contaminates water supply
State and explain two safety precautions necessary for the use of these isotopes in medical procedures.
- reduce exposure time AND lower amount of radiation absorbed
- increase distance between source and hospital staff AND lower amount of radiation reaches staff
Give two reasons why alpha‑emitters are not used as radioactive tracers inside the body.
Highly ionising. Radiation would not reach detector outside body.
