Nuclear Physics

Question 1

What is the size of the nucleus approximately?

Answer 1

10^-15 m

This measurement indicates the nuclear diameter.

Question 2

Who is known for the discovery of the nucleus?

Answer 2

Ernest Rutherford

He made significant contributions to the understanding of atomic structure.

Question 3

What type of radiation did Rutherford use in his experiments?

Answer 3

• Alpha particles
• Beta particles
• Gamma rays

These types of radiation were essential in probing the structure of the atom.

Question 4

What did Rutherford’s experiments lead to the proposal of?

Answer 4

The nuclear model of the atom

This model was based on his findings from alpha particle scattering.

Question 5

True or false: Rutherford believed that the nucleus is positively charged.

Answer 5

TRUE

This is because it repels alpha particles, which also carry a positive charge.

Question 6

What did Rutherford note about alpha particles that were scattered at large angles?

Answer 6

They indicated the presence of a nucleus

This observation was key to developing the nuclear model.

Question 7

What did Rutherford use to probe the structure of the atom?

Answer 7

A narrow beam of alpha particles

This method allowed him to observe scattering patterns.

Question 8

Define alpha (α) radiation.

Answer 8

Easily absorbed radiation consisting of positively charged particles

Alpha radiation is one of the types of radiation emitted by radioactive substances.

Question 9

Define beta (β) radiation.

Answer 9

More penetrating radiation consisting of negatively charged particles

Beta radiation is another type of radiation emitted by radioactive substances.

Question 10

Define gamma (γ) radiation.

Answer 10

Highly penetrating radiation consisting of high energy photons

Gamma radiation is the most penetrating type of radiation discovered.

Question 11

What are the three types of radiation discovered by Rutherford?

Answer 11

• Alpha (α) radiation
• Beta (β) radiation
• Gamma (γ) radiation

Each type has distinct properties and levels of penetration.

Question 12

True or false: Alpha radiation is the most penetrating type of radiation.

Answer 12

FALSE

Gamma radiation is more penetrating than alpha and beta radiation.

Question 13

What effect does a magnetic field have on alpha and beta radiation?

Answer 13

• Deflects alpha (α) radiation in one direction
• Deflects beta (β) radiation in the opposite direction
• No effect on gamma (γ) radiation

The deflection direction indicates the charge of the particles.

Question 14

Why is radiation considered dangerous?

Answer 14

It can ionize air, making it conduct electricity and potentially harm living tissues

Ionizing radiation can lead to cellular damage and increase cancer risk.

Question 15

What is the significance of ionizing air in relation to radiation?

Answer 15

It makes air conduct electricity

This property is used to detect and measure radiation.

Question 16

What is the range in air for α particles compared to β particles?

Answer 16

α particles have a much shorter range in air than β particles

α particles typically travel only a few centimeters in air.

Question 17

What is the effect of γ radiation compared to α and β particles?

Answer 17

γ radiation has a much greater penetrating effect than α or β particles

Photons carry energy and can penetrate materials more effectively.

Question 18

What is the purpose of a cloud chamber in observing radiation?

Answer 18

To visualize the paths of charged particles

The cloud chamber contains air or vapor at low temperature, allowing droplets to form along the paths of ionizing particles.

Question 19

How do the tracks of α particles differ from those of β particles in a cloud chamber?

Answer 19

α particles produce visible tracks of the same length; β particles produce wispy trails

This is due to the greater ionizing ability of α particles compared to β particles.

Question 20

What is the function of the Geiger tube?

Answer 20

To detect ionizing radiation

The Geiger tube contains argon gas at low pressure and allows α and β particles to enter through a thin mica window.

Question 21

Fill in the blank: α radiation is absorbed completely by _______.

Answer 21

paper and thin metal foil

This property makes α radiation less penetrating than β or γ radiation.

Question 22

What thickness of metal is required to absorb β radiation completely?

Answer 22

About 5 mm of metal

This indicates that β radiation is more penetrating than α radiation but less than γ radiation.

Question 23

What is required to absorb γ radiation completely?

Answer 23

Several centimeters of lead

γ radiation is highly penetrating and requires dense materials for effective absorption.

Question 24

What is the relationship between the count rate and the thickness of an absorber in radiation experiments?

Answer 24

Count rate decreases as absorber thickness increases

This relationship is typically represented on a logarithmic scale.

Question 25

What type of **radiation** has a range of only a few centimeters in air?

Answer 25

α radiation ## Footnote The count rate decreases sharply once the tube is beyond the range of α particles.

Question 26

What is the range of **β radiation** in air?

Answer 26

Up to about 1 meter ## Footnote The count rate gradually decreases with increasing distance until it matches the background count rate.

Question 27

What type of **radiation** has an unlimited range in air?

Answer 27

γ radiation ## Footnote The count rate decreases gradually with increasing distance due to the spreading of radiation in all directions.

Question 28

The **inverse square law** applies to which type of radiation?

Answer 28

γ radiation ## Footnote It explains the decrease in the proportion of photons from the source entering the tube with distance.

Question 29

What is the purpose of measuring the **background count rate** in radiation experiments?

Answer 29

To calculate the corrected count rate ## Footnote This is done in the absence of the radiation source.

Question 30

What is the **symbol** for an α particle?

Answer 30

α ## Footnote An α particle consists of 2 protons and 2 neutrons.

Question 31

What is the **charge** of a β particle?

Answer 31

-e ## Footnote A β particle is an electron emitted from a nucleus.

Question 32

What occurs during **β- emission**?

Answer 32

A neutron changes into a proton and emits a β- particle ## Footnote This process increases the atomic number of the nucleus.

Question 33

What is the **symbol** for a positron?

Answer 33

β+ ## Footnote A positron is the antimatter counterpart of an electron.

Question 34

What happens during **β+ emission**?

Answer 34

A proton changes into a neutron and emits a positron ## Footnote This process decreases the atomic number of the nucleus.

Question 35

What is **electron capture** in the context of nuclear reactions?

Answer 35

A process where a proton in the nucleus changes into a neutron, emitting an electron neutrino ## Footnote This occurs when proton-rich nuclides capture an inner-shell electron.

Question 36

What happens to an atom after **electron capture**?

Answer 36

An outer-shell electron fills the inner-shell vacancy, emitting an **X-ray photon** ## Footnote This emission occurs as a result of the transition of electrons between energy levels.

Question 37

What occurs during **gamma (γ) emission**?

Answer 37

No change in the number of protons or neutrons; a γ photon is emitted if excess energy remains after emitting an α or β particle ## Footnote This process helps the nucleus to reach a more stable energy state.

Question 38

What are the **hazards of ionising radiation**?

Answer 38

* Affects living cells * Damages DNA * Can cause cancerous growths ## Footnote Ionising radiation can lead to somatic effects (affecting the individual) and genetic effects (affecting future generations).

Question 39

True or false: There is evidence of a **threshold level** of ionising radiation below which living cells would not be damaged.

Answer 39

FALSE ## Footnote No evidence supports the existence of a safe threshold for ionising radiation exposure.

Question 40

What are the **somatic effects** of exposure to ionising radiation?

Answer 40

* Cell death * Uncontrolled growth * Mutation ## Footnote These effects directly impact the health of the affected individual.

Question 41

What is the purpose of a **film badge** in radiation monitoring?

Answer 41

To monitor exposure to ionising radiation ## Footnote The badge contains photographic film that indicates the level of exposure based on blackening.

Question 42

How does a **film badge** indicate exposure to different types of ionising radiation?

Answer 42

Different areas of the film are covered by absorbers of various materials and thicknesses ## Footnote The blackening of the film upon development reveals the amount of exposure to each radiation type.

Question 43

What happens if a **film badge** is overexposed?

Answer 43

The wearer is not allowed to continue working with the equipment ## Footnote This is a safety measure to prevent excessive exposure to ionising radiation.

Question 44

What is **background radiation**?

Answer 44

Radiation that occurs naturally due to cosmic radiation and from rocks, oil, and air ## Footnote Background radiation varies with location due to local geological features.

Question 45

What is the recommended storage method for **radioactive materials**?

Answer 45

In lead-lined containers ## Footnote Lead lining is necessary to reduce gamma radiation to background levels.

Question 46

What should be used to transfer **solid radioactive sources**?

Answer 46

Handling tools such as tongs or a glove-box ## Footnote These tools help keep the material away from the user to minimize radiation exposure.

Question 47

Fill in the blank: **Liquid and gas sources** should be in _______ to prevent inhalation or skin contact.

Answer 47

sealed containers ## Footnote This ensures safety from exposure to radioactive materials.

Question 48

What happens to the intensity of a **gamma beam** as it passes through an absorber?

Answer 48

It decreases exponentially with the thickness of the absorber ## Footnote If a certain thickness cuts the intensity to half, twice the thickness will cut it to a quarter.

Question 49

What is meant by the **activity** of a radioactive isotope?

Answer 49

The number of nuclei of the isotope that disintegrate per second ## Footnote The unit of activity is the becquerel (Bq), where 1 Bq = 1 disintegration per second.

Question 50

Define the **half-life** of a radioactive isotope.

Answer 50

The time taken for the mass of the isotope to decrease to half the initial mass ## Footnote This is the same as the time taken for the number of nuclei of the isotope to decrease to half the initial number.

Question 51

True or false: The **activity** of a radioactive isotope increases with time.

Answer 51

FALSE ## Footnote The activity decreases with time as the mass of the radioactive isotope decreases due to radioactive decay.

Question 52

What happens to the **mass** of a radioactive isotope over time?

Answer 52

It decreases exponentially ## Footnote The mass decreases to a factor of 0.8 every 1000 seconds, for example.

Question 53

What is the **unit of activity** for a radioactive isotope?

Answer 53

Becquerel (Bq) ## Footnote 1 Bq equals 1 disintegration per second.

Question 54

Fill in the blank: The **activity** of a radioactive isotope is proportional to its _______.

Answer 54

mass ## Footnote As the mass decreases, the activity also decreases.