Aqa Higher Physics P2- Part Two

Front 1

Explain Rutherford scattering and the demise of the plum pudding

Back 1

1804 Dalton-matter was made of tiny spheres ,each element was made up of a different type of "atom"
100 years later JJ Thomson-discovered that electrons could be removed from atoms.Atoms were spheres of positive charge with tiny negative electrons stuck in them
1909 Rutherford and Marsden-fired a beam of alpha particles at thin gold foil.They expected that the positively charged alpha particles would be slightly deflected by the electrons in the plum pudding model.But most of the alpha particles went straight through but the odd one came back at them.

Front 2

Why did the odd alpha particle come straight back ?

Back 2

Because most of the mass of the tail was concentrated at the centre in the nucleus and that the nucleus had a positive charge since it repelled the positive alpha particles.It also showed that most of an atom is just empty space.

Front 3

What are the masses and charge of the parts of an atom ?

Front 4

The number of protons = ?

Back 4

The number of electrons , both have opposite charges.But if electrons are added or removed it becomes a charged particle called an ion

Front 5

What's an isotope, mass number at atomic number

Back 5

Isotopes-Atoms with the same number of protons but a different number of neutrons (1 or two are stable but others are radioactive which means they decay into other elements and give out radiation)
Atomic number-number of protons
Mass number-protons + neutrons

Front 6

Radioactivity is a ?

Back 6

Totally random process

Front 7

Where does background radiation come from ?

Back 7

1) unstable isotopes
2) cosmic rays
3) man made sources

Front 8

What are alpha particles ?

Back 8

-Two neutrons and two protons
-big, heavy, slow moving
-don't penetrate far into materials and are stopped quickly
-strongly ionising (they knock electrons off other atoms)

Front 9

What are beta particles ?

Back 9

-move quite fast and are quite small
-penetrate moderately into materials before colliding
-long range
-moderately ionising
-no mass charge of -1

Front 10

In a nuclear equation and it decays by alpha what happens to the mass and atomic number

Back 10

Atomic number -2
Mass number -4
+ He atomic no=4
mass no=2
+Gamma ray

Front 11

What happens in a nuclear equation with beta decay

Back 11

Atomic number +1
Mass number stays the same
+ electron (0 mass no -1 atomic number)

Front 12

What are gamma rays

Back 12

Very shortwave length EM waves
-they penetrate far into materials without being stopped and pass straight through air
-weakly ionising as they pass through rather than collide with atoms
-no mass or charge

Front 13

The damage radiation caused depends on ?
Which depends on ?

Back 13

Radiation dose which depends on location and occupation (e.g certain ricks can release radioactive gases and people who work as uranium miners and radiographers are exposed to more radiation)

Front 14

What happens to beta and alpha particles when they travel through an electric or magnetic field

Back 14

They will be deflected but in opposite directions as alpha particles have a positive charge but beta particles have a negative charge.Alpha particulars are deflected less because they have a much greater mass even though they feel a greater force as they have a larger charge.

Front 15

Why isn't gamma deflected by electric or magnetic fields

Back 15

Because it has no charge

Front 16

The radioactivity of a sample always decreases over time What is half-life

Back 16

The average time it takes for the number if nuclei in a radioactive isotope sample to halve.Short half life means activity falls quickly because lots of nuclei decay quickly

Front 17

How do you do half life questions

Back 17

Keep dividing the activity of the radioisotope to find out the activity at one half life then 2 etc until you get the number in the question.Then divide how long it has taken to decrease to that activity( given in the question ) by the number of half lives to get the answer

Front 18

How to find the half life sample using a graph

Front 19

How do smoke detectors work

Back 19

A weak source of alpha radiation is placed in the detector , close to two electrodes.This source causes ionisation and a current flows between the electrodes.If there is a fire then the smoke will absorb the radiation-so the current stops and the alarm sounds

Front 20

What are tracers in medicine

Back 20

Short half life -so the radioactivity quickly disappears beta or gamma emitters -so that radiation passes out of the body
E.g iodine

Front 21

What is radiotherapy

Back 21

Gamma rays because high doses will kill all living cells

Front 22

How are surgical instruments and food sterilised

Back 22

Gamma rays-as they will kill all microbes but not damaged like they would be if they were boiled
It needs to be a strong emitter with a long half life so it doesn't need replacing too often

Front 23

How does radiation harm living cells ?
which are the most harmful outside the body and why ?
Which are the most harmful inside the body and why ?

Back 23

1) They enter living cells and collide with molecules causing ionisation which damages or destroys the molecules.If the radiation does not kill the cell it can give a rise to mutant cells-cancer
2)Beta and gamma as it can get inside to the organs whereas alpha can't penetrate the skin
3)alpha as it damages parts of the body in a very localised area but beta and gamma pass straight out

Front 24

What precautions must be taken when handling radioactive materials ?

Back 24

1)use radioactive sources for the shortest time possible so exposure is kept to a minimum
2)handle with tongs
3)Keep far away from the body to decrease the amount of radiation that hits you
4)point it away and don't look directly at it
5)store in a lead box as it absorbs all three types of radiation

Front 25

What happens in a nuclear reactor

Back 25

Nuclear fission-splitting up of big atomic nuclei
Controlled chain reaction , the nuclei split and release energy in the form of heat which heats water to make steam to drive a turbine.The fuel that's split is usually uranium-235 or plutonium-239

Front 26

What happens in a chain reaction in nuclear fission

Back 26

A slow moving neutron is absorbed into the nucleus making the nucleus causing it to split and spit out neutrons which then may hit another nucleus keeping the chain reaction going

Front 27

What are the disadvantages of nuclear power

Back 27

Disposal of waste -difficult and expensive
Decommissioning is costly and takes decades
Carries the risk of radiation leaks

Front 28

What happens in nuclear fusion

Back 28

The joining of small atomic nuclei to create a larger nucleus.It can only happen at a very high temperature and hydrogen can be used as the 'fuel' but you can't hold it at the high temperatures and pressures required as you need an extremely strong magnetic field.It doesn't leave behind waste and releases a lot of energy (more than fission)

Front 29

What happens in the life cycle of stars