P2.5 - Radioactivity

Question 0

What is a radioactive substance?

Answer 0

A substance which contains unstable nuclei that becomes stable by emitting radiation.

Question 1

What are the types of radiation?

Answer 1

• Alpha
• Beta
• Gamma

Question 2

When does a radioactive source decay?

Answer 2

Radioactive decay is a random event.

Question 3

Where does background radiation come from?

Answer 3

It is from radioactive substances in the environment, space or man-made devices such as X-ray machines.

Question 4

Who discovered radioactivity?

Answer 4

Marie and Pierre Curie

Question 5

How was the nuclear model of the atom established?

Answer 5

Using measurements from alpha scattering, the idea was proven that an atom had a positively charged central nucleus where most of the mass of the atom is located?

Question 6

Who initially came up with the nuclear model?

Answer 6

Ernest Rutherford

Question 7

Why was the plum pudding model rejected?

Answer 7

It could not explain why some alpha particles were scattered through large angles.

Question 8

Why was the nuclear model accepted?

Answer 8

The nuclear model explained why alpha particles are scattered and some through large angles.

Question 9

Why must an atom have a positive nucleus based on Rutherford’s results?

Answer 9

The nucleus repelled the positively charged alpha particle.

Question 10

Why must the nucleus be much smaller than the atom?

Answer 10

Most of the alpha particles passed straight through.

Question 11

What is an isotope?

Answer 11

An form of an element with the same number of protons but a different number of neutrons.

Question 12

How does the nucleus of an atom change when it emits alpha particles?

Answer 12

The nucleus loses two protons and two neutrons.

Question 13

How does the nucleus of an atom change when it emits a beta particle?

Answer 13

A neutron changes into a proton.

Question 14

How far can alpha radiation travel?

Answer 14

• A few centimetres in air

- Stopped by a piece of paper

Question 15

What is alpha radiation?

Answer 15

Two protons and two neutrons

Question 16

What is the range of beta radiation?

Answer 16

• A metre in air

- Stopped by a thin sheet of metal

Question 17

What is beta radiation?

Answer 17

Fast moving electrons emitted from the nucleus.

Question 18

What is the range of gamma radiation?

Answer 18

• Unlimited range in air

- Stopped by thick lead

Question 19

What is gamma radiation?

Answer 19

Electromagnetic radiation

Question 20

How is a beam of alpha, beta and gamma radiation separated?

Answer 20

A magnetic or electric field

Question 21

Why are the different types of radiation dangerous?

Answer 21

They ionise substances they pass through which can kill living cells.

Question 22

Why aren’t gamma rays deflected?

Answer 22

Gamma is electromagnetic radiation so it is uncharged.

Question 23

Which type of radiation has the greatest ionising effect?

Answer 23

Alpha

Question 24

What is the half life of a radioactive source?

Answer 24

The average time it takes for the number of nuclei of the isotope in a sample to halve.

Question 25

What is the activity of a radioactive source?

Answer 25

The number of nuclei that decay per second.

Question 26

What factors determine the use of a radioactive isotope?

Answer 26

• Half life

- Type of radiation emitted

Question 27

What type of isotope should be used for monitoring?

Answer 27

An isotope with a long half-life.

Question 28

What are radioactive tracers made of?

Answer 28

Beta or gamma emitters, usually iodine, that last long enough to monitor but not too long to ensure cells aren’t damaged.

Question 29

What is radioactive dating?

Answer 29

A process using uranium or carbon used to determine the age of igneous rocks and wood.

Question 30

What is automatic thickness monitoring?

Answer 30

The use of a beta emitter to regulate the thickness of metal foil.

Question 31

Explain automatic thickness monitoring.

Answer 31

• There is an emitter on one side of the foil and detector on the other.
• If the thickness increase too much, the detector reading drops.
• The detector sends a signal to increase the pressure on the metal sheet making the foil thinner.

Question 32

What is the purpose of a radioactive tracer?

Answer 32

Doctors can see whether there is a blockage in a patient’s kidney.

Question 33

Explain the use of radioactive tracers.

Answer 33

• The patient drinks water containing the radioactive substance.
• A detector is placed against each kidney.
• If the kidney is healthy, the reading goes up then down.
• If not, the reading goes up and stays up.

Question 34

Why is radioactive iodine best for use as a radioactive tracer?

Answer 34

• It only has a half-life of 8 days giving enough time to do the test.
• It emits gamma radiation which can be detected outside the body.
• It decays into a stable product.

Question 35

Explain carbon dating.

Answer 35

• Used to find the age of organic material.
• Organic material contains some radioactive carbon with a half-life of 5600 years.
• When dead, the material stops absorbing carbon meaning the amount of radioactive carbon decreases.
• The count rate from the wood is compared to the rate of living wood.

Question 37

Explain uranium dating.

Answer 37

• Igneous rocks contain radioactive uranium with a half-life of 4500 million years.
• Uranium decays into lead.
• The age is distinguished by comparing the number of atoms of uranium and lead. 1:1 makes the sample 4.5 billion years old.

Question 38

Since you’ve been using these flashcards for free, please consider making a small donation for the hundreds of hours it took to make them.

Answer 38

http://bit.ly/21T6H3W

Thank you and good luck!