Physics Week 1

Question 1

Why is physics important in medical radiation?

Answer 1

It explains how radiation interacts with matter, which is crucial for safe and effective use in medical imaging, therapy, and nuclear medicine.

Question 2

What is radiation?

Answer 2

Energy that travels through space as waves or particles.

Question 3

What is ionising radiation?

Answer 3

Radiation that has enough energy to remove electrons from atoms.

Question 4

What is radioactivity?

Answer 4

The spontaneous emission of particles or energy from unstable atomic nuclei.

Question 5

What is the unit of force in SI?

Answer 5

Newton (N), defined as kg·m/s².

Question 6

What is the Law of Conservation of Energy?

Answer 6

Energy cannot be created or destroyed, only converted from one form to another.

Question 7

What is the equation for mass-energy equivalence?

Answer 7

E=mc^2

Question 8

What keeps electrons in orbit around the nucleus?

Answer 8

The attractive electromagnetic force between electrons and the positively charged nucleus.

Question 9

What holds protons and neutrons together in the nucleus?

Answer 9

The strong nuclear force.

Question 10

What is binding energy?

Answer 10

Energy required to remove an electron from its shell or to disassemble the nucleus.

Question 11

What does the atomic number (Z) represent?

Answer 11

The number of protons.

Question 12

What does the mass number (A) represent?

Answer 12

The sum of protons and neutrons.

Question 13

What is an isotope?

Answer 13

Atoms of the same element with different numbers of neutrons.

Question 14

What is the maximum number of electrons in a shell?

Answer 14

2n^2, where n is the shell number.

Question 15

Which shell has the highest binding energy?

Answer 15

K shell (closest to the nucleus).

Question 16

What happens when an electron jumps to a higher shell?

Answer 16

The atom enters an excited state.

Question 17

What happens when an electron returns to a lower shell?

Answer 17

Energy is released, usually as a photon.

Question 18

What is mass defect?

Answer 18

The difference between the mass of an atom and the total mass of its separate nucleons.

Question 19

How is binding energy calculated from mass defect?

Answer 19

E(b) = Δm⋅c^2

Question 20

What is the most stable nucleus and why?

Answer 20

Iron-56; it has the highest binding energy per nucleon.

Question 21

What is the SI unit of radioactivity?

Answer 21

Becquerel (Bq) = 1 decay per second.

Question 22

What is the SI unit of absorbed dose?

Answer 22

Gray (Gy) = 1 J/kg.

Question 23

What is the SI unit of equivalent dose?

Answer 23

Sievert (Sv) = weighted dose for biological effect.

Question 24

What is air kerma?

Answer 24

Kinetic energy released per unit mass in air; measured in Gray (Gy).

Question 25

What is the difference between radiation actibity, the absorbed dose, equivalent dose, and effective dose?

Answer 25

radiation activity: Rate of emission from a radioactive source. absorbed dose: the absorbed dose of radiation (measured in Gy) Equivalent dose: the amount of radiation absorbed relative to the type of radiation (Wr factor) Effective dose: the amount of radiation absorbed by a particular type of radiation in a particular tissue (Wt factor).

Question 26

What is the difference between ionsing and non-ionisng radiation?

Answer 26

Ionising radiation: A photon with energy (hf) has energy greater than the binding energy of the atom. Electrons absorb this energy and are removed from the atom. Due to the law of consevertion energy, the energy is released as an electron and as a secondary characteristic photon which contains energy in the from of hf-EB. Non-ionising radiation: The photon does not contain enough energy to displace the electron from the atom. But in some instances, it can excite the atom from its ground state to an excited state. The electron jumps to a lower energy level, leaving a vacancy in the lower orbital. Because the atom wants to remain stable, it jumps back down and releases energy known as the difference between the two energy levels (inital-final).

Question 27

Describe the difference and relationship between energy, work, and force.

Answer 27

- energy is teh ability of a system to do work. - work is the amount of force applied to a system to make it move some distance x. - force is the action of one body on another that changed its state of rest or motion. F = ma

Question 28

What are the four types of force?

Answer 28

- gravitational - attrraction between two bodies of mass. - electromagnetic - holds electrons in their orbital shells. - strong nuclear - holds the nucleas together. - weak nuclear - important in radioactive decay as there is too high of a ratio of protons: neutrons.

Question 29

What is the law of conservertion energy?

Answer 29

- The total energy in a system does not change but the way it is expressed can be transformed.

Question 30

What are the two types of energy?

Answer 30

- Potential energy: Energy stored in an object due to its position or state. E.g, a skydiver standing 100m above ground with a mass. - Kinetic energy: The energy of an object that is in motion. E.g, a skydiver falling.