P4

Question 1

What is the radius of an atom

Answer 1

Around 1×10^ -10 m

Question 2

What do radioactive substances always give out and from where

Answer 2

– Radiation from nuclei of atoms

Question 3

What does a short half life mean and why does it occur

Answer 3

– Activity falls quickly because the nuclei are very unstable and rapidly decay

Question 4

Describe the safety of sources with a short half life

Answer 4

– Can be dangerous because of the high amount of radiation they omitted the start
– quickly become safe

Question 5

What does a long half life of a substance mean and why does it occur

Answer 5

– Activity falls more slowly because most of the nuclei don’t decay for a long time

Question 6

Describe the danger of substances with a long half life

Answer 6

– Source just sits there are releasing small amounts of radiation for a long time
– can be dangerous because nearby areas are exposed to radiation for (millions of) years

Question 7

What is background radiation and what should you always do with it when experimenting to avoid what

Answer 7

– The low-level radiation that is around us all of the time

– should measure and subtract the background radiation from your results to avoid systematic errors

Question 8

Where does background radiation come from

Answer 8

– Radioactivity of naturally occurring on stable isotopes which are all around us – in there, food, building materials and rocks under our feet
– radiation from space which is known as cosmic rays – mostly from Sun – earths atmosphere protect us from much of this radiation
– radiation due to human activity e.g. fallout from nuclear explosions or nuclear waste – represents tiny proportion of the total background radiation

Question 9

What does radiation dose tell you and what is it measured in

Answer 9

– The risk of harm to body tissues due to exposure to radiation
– sieverts (Sv)

Question 10

What is the dose of background radiation often measured in and why

Answer 10

– millisieverts

– the dose from background radiation is small

Question 11

What is your radiation dose affected by

Answer 11

– Where you live
– whether you have a job that involves radiation
– other factors such as having x-rays

Question 12

What is irradiation

Answer 12

Exposure to radiation

Question 13

What does and doesn’t irradiating something do

Answer 13

– Exposes it to the radioactive source

– doesn’t make it radioactive

Question 14

What are ways of reducing irradiation when working with radioactive sources

Answer 14

– Keeping sources in lead lined boxes
– standing behind barriers
– being in a different room and using remote-controlled arms

Question 15

What is a substance said to be if unwonted radioactive atoms get onto or into it and what is an example

Answer 15

Contaminated

If you touch a radioactive source without wearing gloves your hands would be contaminated

Question 16

Why is radioactive contamination especially dangerous

Answer 16

Radioactive particles could get inside your body

Question 17

What can be used to reduce radioactive contamination

Answer 17

Gloves and tongs when handling sources to avoid particles getting stuck to your skin or and your nails

Some industrial workers wear protective suits to stop them breathing in particles

Question 18

What are the most dangerous type of radioactive sources outside of the body and why

Answer 18

– Beta and gamma
– they can penetrate the body and get into delicate organs
– alpha less angels because it can’t penetrate skin and is easily blocked by small airgap
– high levels of irritation from all sources are dangerous but especially ones that emit beta and gamma

Question 19

Which type of radioactive source is the most and least dangerous inside of the body and why

Answer 19

– Alpha
– they do all of their damaged in a very localised area so contamination rather than irritation is the major concern
– Beta less damaging inside the body as radiation is absorbed over a wide area and some passes out of body altogether
– gamma least dangerous inside body as they mostly pass straight through – lowest ionising power

Question 20

Why is It’s important that research about different types of radiation and how they affect our bodies is published and what happens to the data before publishing and what does this lead to

Answer 20

– It means we can understand about how different types affect our bodies – we can protect ourselves when using them
– peer reviews – quickly become accepted – many improvements in our use of radioactive sources

Question 21

What is nuclear fission

Answer 21

A type of nuclear reaction that is used to release energy from large and unstable items e.g. uranium or plutonium by splitting them into smaller atoms

Question 22

What usually has to happen to the nucleus before it will split and what does this mean

Answer 22

– Absorb a neutron

– spontaneous (and force) sufficient rarely happens

Question 23

LOOK AT NUCLEAR FISSION DIAGRAM

Answer 23

.

Question 24

What happens when the atom splits

Answer 24

Its forms two new lighter elements that are roughly the same size and have some energy in their kinetic energy stores

Two or three neutrons also released – if any of these neutrons are moving slow enough to be absorbed by another nucleus, they can cause more fission to occur – chain reaction

Question 25

What happens to the energy not transferred to the kinetic energy stores of the products of nuclear fission

Answer 25

Carried away by gamma rays

Question 26

What can the energy carried away by gamma rays and in kinetic energy stores of remaining three neutrons and other decay products of nuclear fission be used for

Answer 26

To heat water, making steam to turn turbines and generators

Question 27

What is the amount of energy produced by fission in a nuclear reaction controlled by and how is this done

Answer 27

– Changing how quickly the chain reaction can occur
– using control rods which when lowered and raised inside a nuclear reactor, absorb neutrons – slows down the chain reaction and controls the amount of energy released

Question 28

How do nuclear weapons work

Answer 28

Uncontrolled chain reactions quickly lead to lots of energy being released as an explosion

Question 29

What happens during nuclear fusion And what is an example

Answer 29

Two light nuclei collide at high speed and join to create a larger, heavier nucleus

E.g. hydrogen nuclei confused to produce a helium nucleus

Question 30

Describe the heavier nucleus formed in nuclear fusion

Answer 30

– Not as much mess as the two separate nuclei did – some of the mass of the light to nuclei converted to energy – energy then released as radiation

Question 31

Does fusion release a lot or a little bit of energy

Answer 31

A lot

Question 32

Have scientists so far found a way of using fusion to generate energy for us to use and why

Answer 32

No – the temperatures and pressures needed for fusion are so high that fusion reactors are really hard and expensive to build