Radiation

Question 1

Explain why this γ-emission does not affect the numbers in the equation.

Answer 1

has no charge

Question 2

Suggest one reason why a nucleus of thallium-208 is unstable.

Answer 2

excess neutrons

Question 3

How to calculate neutrons.

Answer 3

Top-Bottom=Neutrons

Question 4

How to calculate electrons.

Answer 4

Same as protons in a neutral atom

Question 5

From the data given for positions A, B and C, deduce the type of emissions coming from the radioactive source. Explain your reasoning.

Answer 5

B- gamma, not deflected, not charged
C- beta, charged particles deflected (L rule)
A- background detected here

Question 6

State the nature of γ-rays

Answer 6

electromagnetic radiation of high frequency and short wavelength

Question 7

Compare the deflections of the paths of the two types of particle.

Answer 7

deflect in opp directions
β deflected more

Question 8

Describe the path of the beta particles.

Answer 8

curved path
deflected towards positively charged plate

Question 9

State the nature of an α-particle.

Answer 9

2 protons, 2 neutrons

Question 10

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.

Answer 10

α towards negative (plate)
β towards positive (plate)

Question 11

State what is meant by the term isotopes

Answer 11

Different version of the same element.
Same number of protons.
Different number of neutrons (,,a diff nucleon number)

Question 12

State and explain the type of radiation that must be emitted by the isotope for the leak to be detected.

Answer 12

Gamma, can penetrate through the surface and ground and reach the detector unlike the other radiation which are stopped before that

Question 13

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.

Answer 13

long enough to find leak
short enough to disappear quickly

Question 14

What is alpha stopped by?

Answer 14

thin sheet of paper

Question 15

What is beta stopped by?

Answer 15

thin sheet of aluminium

Question 16

What is gamma stopped by?

Answer 16

thick lead or concrete

Question 17

What is the alpha charge?

Answer 17

+ 3.2 × 10–19

Question 18

What is the beta charge?

Answer 18

-1.6 x 10 -19

Question 19

The radiation is said to be ionising. Explain what this means

Answer 19

atoms lose electrons

Question 20

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)

Answer 20

α travels more slowly, loses energy with each collision so range is short

α is charged, somore ionising because it has greater charge

Question 21

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.

Answer 21

Low count rate due to background.
Slightly less due to random decaying fashion.
High due to emission from source.

Question 22

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.

Answer 22

Decay of source slowed down =
Activity decreased due to less radioctive nuclei

Question 23

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.

Answer 23

decreases, not completely absorbed

Question 24

Suggest why the paths of the particles in the magnetic field are curved.

Answer 24

the force on the particles is perpendicular to their paths

Question 25

Describe the results from this scattering experiment and explain what they show about the structure of atoms.

Answer 25

straight->mostly empty space, nucleus tiny small number deflected through large angles-> most mass in nucleus, nucleus is positive

Question 26

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

Answer 26

number of protons and neutrons

Question 27

Explain why α-particles are more strongly ionising than β-particles

Answer 27

more ke, more charge

Question 28

explain the advantage of this long half-life for the use and safe disposal of a household smoke alarm.

Answer 28

low activity, so not hazardous to humans, disposal of old detectors is easy and cheap

Question 29

Household smoke alarm: type of radioactive emission- explanation- Half-life-

Answer 29

alpha, highly ionising, 100 years

Question 30

measuring the thickness of aluminium strips produced in a factory type of radioactive emission- explanation- half-life-

Answer 30

beta absorption depends on thickness of aluminium any number of years

Question 31

State two different sources of background radiation.

Answer 31

radon gas (in the air) rocks OR buildings food OR drink cosmic rays

Question 32

Suggest why isotope X2 is stable whereas X1 is not stable.

Answer 32

(X2) has fewer (excess) neutrons

Question 33

Suggest one reason why isotopes with very short half-lives are especially hazardous.

Answer 33

high dose (of radiation) in short time

Question 34

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.

Answer 34

2 1H + 2 1H → 3 2He + 1 0 n

Question 35

Nuclide equation for fusion.

Answer 35

combine, make note of any particles formed

Question 36

During β-decay, one of the neutrons in the nucleus changes. Explain how charge is conserved during this change.

Answer 36

charge on neutron = 0 OR total charge on products = 0 charge on proton = +1 AND charge on electron = –1

Question 37

Describe the composition and structure of a neutral atom of uranium‐235.

Answer 37

Very small nucleus surrounded by electrons in the orbit. This many protons=the same number of electrons. This many neutrons.

Question 38

Nuclear fission nuclide equation.

Answer 38

Minusing, make note of any particles formed

Question 39

State the proton number, nucleon number, electron number and the value of the charge on an beta-particle.

Answer 39

0 protons, o nucleons, 1 electron, -1

Question 40

How to remember the speeds of the different ionising radiation

Answer 40

She believes we (community) remember sun brighten

Question 41

Beta decay?

Answer 41

plus one proton, one fewer neutron 0 -1 β

Question 42

Alpha decay?

Answer 42

minus 2 protons and 4 nucleons 4 2 α.

Question 43

Describe how the americium-241 ionises air

Answer 43

alpha emitted hits air molecules and remove electrons from molecules

Question 44

Explain why an extremely high temperature is needed when forcing these two nuclei together.

Answer 44

same charge, repels, high quantity of energy to do so...

Question 45

β-particles ionise the air they pass through less strongly than the same number of αparticles. Suggest why this is so.

Answer 45

smaller charge travel faster (unlikely to hit) force on electrons is less

Question 46

Suggest reasons for using an α‐particle emitter in a smoke detector

Answer 46

highly ionizing, ionize air more easily short range in air, stopped by smoke do not travel out and cause harm (safe because short range)

Question 47

Explain why the radioactive isotope does not have a very short half-life.

Answer 47

(very short half-life) doesn’t allow time for detection before activity has dropped to too low a level

Question 48

Explain why the radioactive isotope does have a very long half-life.

Answer 48

(very long half-life) contaminates water supply

Question 49

State and explain two safety precautions necessary for the use of these isotopes in medical procedures.

Answer 49

- reduce exposure time AND lower amount of radiation absorbed - increase distance between source and hospital staff AND lower amount of radiation reaches staff

Question 50

Give two reasons why alpha‑emitters are not used as radioactive tracers inside the body.

Answer 50

Highly ionising. Radiation would not reach detector outside body.