Nuclear definitions

Question 1

What conclusion can we draw from the observation that most alpha particles passed straight through the foil with no deflection in the Rutherford scattering experiment?

Answer 1

The atom is mostly empty space.

Question 2

What conclusion can we draw from the observation that a small amount of particles were deflected by a large angle in the Rutherford scattering experiment?

Answer 2

The centre of the atom is positively charged.

Question 3

What conclusion can we draw from the observation that very few particles were deflected back by more than 90 degrees in the Rutherford scattering experiment?

Answer 3

The centre of the atom is very dense.

Question 4

Alpha radiation information

Answer 4

Range: 2 - 10 cm in air
Highly ionising
Deflected by electric and magnetic fields
Absorbed by paper

Question 5

Beta radiation information

Answer 5

Range of around 1 m in air
Weakly ionising
Deflected by electric and magnetic fields
Absorbed by aluminium foil

Question 6

Gamma radiation information

Answer 6

Infinite range - follows inverse square law
Very weakly ionising
Not deflected by electric and magnetic fields
Absorbed by several metres of concrete or several inches of lead

Question 7

What are the uses of gamma radiation as a detector?

Answer 7

A radioactive source with a short half-life (to reduce exposure), which emits gamma radiation, can be injected into a patient and the gamma radiation can be detected using gamma cameras in order to help diagnose patients.

Question 8

What are the uses of gamma radiation to sterilise surgical equipment?

Answer 8

Gamma radiation will kill any bacteria present on the equipment.

Question 9

What are the uses of gamma radiation in radiation therapy?

Answer 9

Gamma radiation can be used to kill cancerous cells in a targeted region of the body such as a tumour, however, it will also kill any healthy cells in that region.

Question 10

What safety precautions should be used when handling radioactive sources?

Answer 10

• using long handled tongs to move the source
• storing the source in a lead-lined container when not in use
• keeping the source as far away as possible from yourself and others
• never pointing the source towards others

Question 11

What are the sources of background radiation?

Answer 11

• radon gas, which is released from rocks
• artificial sources, caused by nuclear weapons testing and nuclear meltdowns
• cosmic rays, enter the Earth’s atmosphere from space
• rocks containing naturally occurring radioactive isotopes

Question 12

What is the decay constant?

Answer 12

The probability of a nucleus decaying per unit time.

Question 13

What is the half-life?

Answer 13

The time taken for the number of nuclei to halve.