Define background radiation .

Background radiation is low levels of radiation from environmental sources, which are always present around us.

Name three natural sources of background radiation.

Radon gas from rocks and soil Cosmic rays from space Carbon-14 in biological material Radioactive material in food and drink

Name three man-made sources of background radiation.

Medical sources (X-rays, CT scans, radioactive tracers, radiation therapy) Nuclear waste Nuclear fallout from nuclear weapons Nuclear accidents

Why is radon gas from rocks and soil considered particularly dangerous?

Radon gas is an alpha emitter , and alpha radiation is especially dangerous if inhaled into the lungs in large quantities.

How is the corrected count rate obtained in a radioactivity experiment?

By taking a reading with no radioactive source present , then subtracting this background radiation value from the reading taken with the source present .

Radiation is measured in counts per second in a unit called the .......... .

Radiation is measured in counts per second in a unit called the Becquerel .

True or False? A half-life graph that tends towards zero as time increases has correctly accounted for background radiation.

False. A half-life graph should tend towards a value higher than zero if background radiation has not been subtracted, since the detector will always register background counts even after the source has fully decayed.

What is an alpha particle ?

An alpha particle is a high energy particle made up of two protons and two neutrons , the same composition as a helium nucleus.

What is a beta-minus particle ?

A beta-minus particle is a high energy electron emitted from the nucleus, from a nucleus that has too many neutrons .

Why are alpha particles usually emitted from a nucleus?

Alpha particles are usually emitted from nuclei that are too large , helping the nucleus become more stable.

What is a gamma ray , and why is it emitted?

A gamma ray is a high energy electromagnetic wave , emitted by a nucleus that needs to lose energy .

Describe the ionising and penetrating power of beta radiation, and state what stops it.

Beta is moderately ionising (due to its charge of +1 e ) and moderately penetrating , with a range of around 20 cm to 3 m in air. It can be stopped by a few millimetres of aluminium foil.

When radiation passes close to an atom, it can knock out electrons, a process called .......... .

When radiation passes close to an atom, it can knock out electrons, a process called ionising (ionisation).

True or False? Beta radiation is more ionising than alpha radiation because it carries more energy overall.

False. Beta is less ionising than alpha. Beta only causes moderate ionisation and damage, whereas alpha, despite having a lower penetrating power, causes much greater ionisation.

How does the proton number and nucleon number of a nucleus change during alpha decay ?

Proton (atomic) number decreases by 2 Nucleon (mass) number decreases by 4

Why is a beta-minus particle given an atomic number of −1 in a nuclear decay equation?

Atomic number is being used to measure charge in the equation. Protons are positive and have positive atomic numbers, so the negatively charged electron (beta particle) is assigned an atomic number of −1 .

How does gamma decay affect the mass number and atomic number of a nucleus?

Gamma decay does not change the mass number or atomic number of the nucleus. It only reduces the energy of the nucleus.

Define how nuclear equations must balance.

In a nuclear equation , the sum of the mass (upper) numbers on the left must equal the sum on the right, and the sum of the atomic (lower) numbers on the left must equal the sum on the right.

During gamma decay, the nucleus emits a gamma ray that carries energy but has no .......... or .......... .

During gamma decay, the nucleus emits a gamma ray that carries energy but has no mass or charge .

True or False? A nucleus that undergoes gamma decay becomes a different element.

False. Gamma decay does not change the proton number or nucleon number of the nucleus, so the nucleus remains the same element , just less energetic.

In Core Practical 15, what are the independent and dependent variables?

Independent variable: thickness of lead Dependent variable: count rate

Name three control variables in Core Practical 15 (investigating gamma absorption).

Radioactive source used Distance of the GM tube from the source Location / background radiation level

Why must background radiation be measured before starting Core Practical 15?

So that the average background count rate can be recorded and later accounted for, ensuring the results reflect only the radiation absorbed from the source .

How is the required thickness of lead to absorb the gamma radiation determined from the results?

If the count rate over the interval falls to background levels (allowing for a little random variation), the radiation has all been absorbed at that thickness.

State two safety precautions to take when handling the radioactive source in Core Practical 15.

Keep the source in a lead-lined container when not in use Keep a good distance (around a metre ) between yourself and the source when it is in use Handle the source with tweezers/tongs , pointing it away from you Wash your hands and remove your outer layer of clothing after handling it

To reduce systematic error, all runs of Core Practical 15 should be conducted in the same .......... to avoid changes in background radiation levels.

To reduce systematic error, all runs of Core Practical 15 should be conducted in the same location to avoid changes in background radiation levels.

True or False? Each count rate reading in Core Practical 15 should be taken only once, to save time.

False. Three readings should be taken at each distance/thickness (repeated three times ) to improve reliability, since radioactive decay is random.

Define radioactive decay .

Radioactive decay is the spontaneous disintegration of a nucleus to form a more stable nucleus, resulting in the emission of an alpha, beta or gamma particle.

Define a spontaneous process.

A spontaneous process is one which cannot be influenced by environmental factors, such as temperature, pressure or chemical conditions.

Define a random process (in the context of nuclear decay).

A random process is one in which the exact time of decay of a nucleus cannot be predicted.

How does the count rate of a GM tube provide evidence for the randomness of radioactive decay?

When a GM tube is placed near a source, the counts are found to be irregular and cannot be predicted, since each count represents the decay of an individual unstable nucleus.

If the decay of an individual nucleus cannot be predicted, how can the behaviour of a large sample of nuclei still be predicted?

Each nucleus has a constant probability of decaying in a given time, so although individual decays are random, the behaviour of the entire group can be predicted statistically .

True or False? Increasing the temperature of a radioactive sample increases its rate of decay.

False. Radioactive decay is a spontaneous process, meaning it is not affected by environmental factors such as temperature, pressure or chemical conditions.

Define the decay constant λ.

The decay constant is the probability, per second, that a given nucleus will decay.

Half-life is the time taken for half the number of nuclei in a sample to decay.

How are half-life and the decay constant related?

Half-life and the decay constant are inversely proportional . The shorter the half-life, the larger the decay constant, and the faster the decay.

An activity of one Becquerel is equal to .......... per second.

An activity of one Becquerel is equal to one decay per second.

True or False? When a time equal to one half-life has passed, the activity of a sample falls to zero.

False. The activity halves , it does not fall to zero. Radioactive decay is exponential, so the number of nuclei (and activity) falls rapidly but never reaches zero.

International A Level (IAL)PhysicsEdexcelFlashcards5. Thermodynamics, Radiation, Oscillations & CosmologyRadioactivity Decay

Radioactivity Decay (Edexcel International A Level (IAL) Physics): Flashcards

Exam code: YPH11

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FrontBackground Radiation
Define background radiation.
FrontBackground Radiation
Name three natural sources of background radiation.
BackBackground Radiation
Radon gas from rocks and soil
Cosmic rays from space
Carbon-14 in biological material
Radioactive material in food and drink
FrontBackground Radiation
Name three man-made sources of background radiation.
BackBackground Radiation
Medical sources (X-rays, CT scans, radioactive tracers, radiation therapy)
Nuclear waste
Nuclear fallout from nuclear weapons
Nuclear accidents

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Cards in this collection (40)

Define background radiation.
Background radiation is low levels of radiation from environmental sources, which are always present around us.
Name three natural sources of background radiation.
- Radon gas from rocks and soil
- Cosmic rays from space
- Carbon-14 in biological material
- Radioactive material in food and drink
Name three man-made sources of background radiation.
- Medical sources (X-rays, CT scans, radioactive tracers, radiation therapy)
- Nuclear waste
- Nuclear fallout from nuclear weapons
- Nuclear accidents
Why is radon gas from rocks and soil considered particularly dangerous?
Radon gas is an alpha emitter, and alpha radiation is especially dangerous if inhaled into the lungs in large quantities.
How is the corrected count rate obtained in a radioactivity experiment?
By taking a reading with no radioactive source present, then subtracting this background radiation value from the reading taken with the source present.
Radiation is measured in counts per second in a unit called the ...........
Radiation is measured in counts per second in a unit called the Becquerel.
True or False?
A half-life graph that tends towards zero as time increases has correctly accounted for background radiation.
False.
A half-life graph should tend towards a value higher than zero if background radiation has not been subtracted, since the detector will always register background counts even after the source has fully decayed.
What is an alpha particle?
An alpha particle is a high energy particle made up of two protons and two neutrons, the same composition as a helium nucleus.
What is a beta-minus particle?
A beta-minus particle is a high energy electron emitted from the nucleus, from a nucleus that has too many neutrons.
Why are alpha particles usually emitted from a nucleus?
Alpha particles are usually emitted from nuclei that are too large, helping the nucleus become more stable.
What is a gamma ray, and why is it emitted?
A gamma ray is a high energy electromagnetic wave, emitted by a nucleus that needs to lose energy.
Describe the ionising and penetrating power of beta radiation, and state what stops it.
Beta is moderately ionising (due to its charge of +1e) and moderately penetrating, with a range of around 20 cm to 3 m in air. It can be stopped by a few millimetres of aluminium foil.
When radiation passes close to an atom, it can knock out electrons, a process called ...........
When radiation passes close to an atom, it can knock out electrons, a process called ionising (ionisation).
True or False?
Beta radiation is more ionising than alpha radiation because it carries more energy overall.
False.
Beta is less ionising than alpha. Beta only causes moderate ionisation and damage, whereas alpha, despite having a lower penetrating power, causes much greater ionisation.
How does the proton number and nucleon number of a nucleus change during alpha decay?
- Proton (atomic) number decreases by 2
- Nucleon (mass) number decreases by 4
Why is a beta-minus particle given an atomic number of −1 in a nuclear decay equation?
Atomic number is being used to measure charge in the equation. Protons are positive and have positive atomic numbers, so the negatively charged electron (beta particle) is assigned an atomic number of −1.
How does gamma decay affect the mass number and atomic number of a nucleus?
Gamma decay does not change the mass number or atomic number of the nucleus. It only reduces the energy of the nucleus.
Define how nuclear equations must balance.
In a nuclear equation, the sum of the mass (upper) numbers on the left must equal the sum on the right, and the sum of the atomic (lower) numbers on the left must equal the sum on the right.
During gamma decay, the nucleus emits a gamma ray that carries energy but has no .......... or ...........
During gamma decay, the nucleus emits a gamma ray that carries energy but has no mass or charge.
True or False?
A nucleus that undergoes gamma decay becomes a different element.
False.
Gamma decay does not change the proton number or nucleon number of the nucleus, so the nucleus remains the same element, just less energetic.
In Core Practical 15, what are the independent and dependent variables?
- Independent variable: thickness of lead
- Dependent variable: count rate
Name three control variables in Core Practical 15 (investigating gamma absorption).
- Radioactive source used
- Distance of the GM tube from the source
- Location / background radiation level
Why must background radiation be measured before starting Core Practical 15?
So that the average background count rate can be recorded and later accounted for, ensuring the results reflect only the radiation absorbed from the source.
How is the required thickness of lead to absorb the gamma radiation determined from the results?
If the count rate over the interval falls to background levels (allowing for a little random variation), the radiation has all been absorbed at that thickness.
State two safety precautions to take when handling the radioactive source in Core Practical 15.
- Keep the source in a lead-lined container when not in use
- Keep a good distance (around a metre) between yourself and the source when it is in use
- Handle the source with tweezers/tongs, pointing it away from you
- Wash your hands and remove your outer layer of clothing after handling it
To reduce systematic error, all runs of Core Practical 15 should be conducted in the same .......... to avoid changes in background radiation levels.
To reduce systematic error, all runs of Core Practical 15 should be conducted in the same location to avoid changes in background radiation levels.
True or False?
Each count rate reading in Core Practical 15 should be taken only once, to save time.
False.
Three readings should be taken at each distance/thickness (repeated three times) to improve reliability, since radioactive decay is random.
Define radioactive decay.
Radioactive decay is the spontaneous disintegration of a nucleus to form a more stable nucleus, resulting in the emission of an alpha, beta or gamma particle.
Define a spontaneous process.
A spontaneous process is one which cannot be influenced by environmental factors, such as temperature, pressure or chemical conditions.
Define a random process (in the context of nuclear decay).
A random process is one in which the exact time of decay of a nucleus cannot be predicted.
How does the count rate of a GM tube provide evidence for the randomness of radioactive decay?
When a GM tube is placed near a source, the counts are found to be irregular and cannot be predicted, since each count represents the decay of an individual unstable nucleus.
If the decay of an individual nucleus cannot be predicted, how can the behaviour of a large sample of nuclei still be predicted?
Each nucleus has a constant probability of decaying in a given time, so although individual decays are random, the behaviour of the entire group can be predicted statistically.
True or False?
Increasing the temperature of a radioactive sample increases its rate of decay.
False.
Radioactive decay is a spontaneous process, meaning it is not affected by environmental factors such as temperature, pressure or chemical conditions.
Define the decay constant λ.
The decay constant is the probability, per second, that a given nucleus will decay.
Define half-life.
Half-life is the time taken for half the number of nuclei in a sample to decay.
State the equation linking activity A, the decay constant λ and the number of remaining nuclei N.
$A = \frac{Δ N}{Δ t} = - λ N$
Where A is measured in Becquerels (Bq).
State the radioactive decay equation for the number of undecayed nuclei N remaining after time t.
$N = N_{0} e^{- λ t}$
Where N₀ is the initial number of undecayed nuclei and λ is the decay constant.
How are half-life and the decay constant related?
Half-life and the decay constant are inversely proportional. The shorter the half-life, the larger the decay constant, and the faster the decay.
An activity of one Becquerel is equal to .......... per second.
An activity of one Becquerel is equal to one decay per second.
True or False?
When a time equal to one half-life has passed, the activity of a sample falls to zero.
False.
The activity halves, it does not fall to zero. Radioactive decay is exponential, so the number of nuclei (and activity) falls rapidly but never reaches zero.

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