Radiation

Question 1

What are isotopes

Answer 1

Isotopes are atoms with different numbers of electrons

Question 2

What does radioactive mean

Answer 2

Consisting of unstable isotopes that can decay

Question 3

What is alpha decay?

Answer 3

Alpha decay is when an unstable nuclei shoots out two protons and neutrons to become more stable

Question 4

What is an alpha particle?

Answer 4

Helium NUCLEUS, not atom.

Question 5

Alpha particles are very large, how does this affect their properties?

Answer 5

• They are very ionising
• Have low penetrating power (can be absorbed easily, travels a few centimetre in air)
• Stopped by paper sheet

Question 6

What is the charge of an alpha particle?

Answer 6

+2

Question 7

What is beta decay?

Answer 7

Beta decay is when a neutron within the nucleus decays into a proton and electron.

The proton stays within the nucleus however the electron is emitted at high speeds.

Question 8

Beta particles (electrons) are small, how does this affect their properties?

Answer 8

• Moderately ionising
• Moderately penetrating
• Stopped by aluminium sheet

Question 9

What is the charge of a beta particle?

Answer 9

-1

Question 10

What are gamma rays?

Answer 10

Waves of pure (electromagnetic) energy passes through the nucleus

Question 11

Do gamma rays affect the mass of the nucleus?

Answer 11

No

Question 12

When are gamma rays often emitted?

Answer 12

After alpha or beta radiation

Question 13

Properties of gamma rays?

Answer 13

• Pass through materials
• Weakly ionising
• Lead/ many sheets of metal stop it.

Question 14

What is emission of neutron?

Answer 14

When the unstable nuclei has too many neutrons, it ejects one to become more stable

Question 15

What type of process is (radioactive) decay?

Answer 15

Random

Question 16

What is activity?

Answer 16

Overall rate of decay of ALL isotopes in our sample (rate at which unstable nucleus decay)

Question 17

What is activity measured in?

Answer 17

Becquerels (Bq)

Question 18

What is 1Bq equal to?

Answer 18

1Bq= 1 decay per second

Question 19

What is half life?

Answer 19

Half life is the time taken for half of the radioactive nuclei to decay OR it is the amount of time it takes for the activity to half

Question 20

How can we find the activity?

Answer 20

Using a Geiger-Muller tube and counter.

Question 21

What does the Geiger-Muller tube and counter do?

Answer 21

Records all the decays that reach them each second.

Alpha, Beta and Gamma rays are all recorded as ‘count rate’ to find activity

Question 22

What is count rate?

Answer 22

Count rate is the number of decays per second

Question 23

How do smoke detectors use radioactivity?

Answer 23

Smoke detectors contain an alpha particle inside, which ionises the air and makes a current.

When smoke blocks/absorbs the alpha particle, it triggers the alarm as a sensor no longer detects the alpha(current)

Question 24

Why are alpha particles used for smoke detectors and not beta/gamma?

Answer 24

Alpha particles are easily absorbed and very ionising.

Beta and Gamma aren’t ionising enough and aren’t as easily absorbed.

Question 25

How are beta particles used to measure the thickness of a material?

Answer 25

When a material moves above a beta source, some beta particles will be absorbed but most will penetrate.

Question 26

What happens when beta particles are used against THICKER materials?

Answer 26

Count rate DECREASES

Question 27

What happens when beta particles are used against THINNER materials?

Answer 27

Count rate INCREASES

Question 28

Why are beta particles used for measuring thickness of materials?

Answer 28

The material only partially absorbs it. Alpha particles would be fully absorbed and Gamma particles would be detected no matter the thickness