P4 e-h Higher Flashcards
What are alpha particles made up of?
An alpha particle is made up of 2 protons and 2 neutrons.
This is the same as a helium nucleus.
What are beta particles made up of?
A beta particle is a fast moving electron.
What is gamma radiation made up of?
Gamma radiation is high frequency electromagnetic waves.
What charge do alpha particles have?
Alpha particles are positively charged as they are only made of protons (positive) and neutrons (neutral).
What charge do beta particles have?
Beta particles are negative as they are electrons.
What is the name for the number of radioactive decays per second?
The ‘activity’. If something is very ‘active’, then there are a lot of decays per second.
Give an example of how alpha radiation can be useful.
Alpha radiation is useful in smoke alarms.
The alpha particles are stopped by the smoke and this causes the currnet in the alarm to drop and the alarm goes off.
Give an example of how beta radiation can be useful.
Beta radiation is useful paper mills.
The amount of beta that gets through depends on how thick the paper is, so adjustments can be made to the paper rolling machinery.
Give an example of how gamma radiation can be useful.
Gamma is useful for sterilising medical equiment, finding leaks/blockages in underground pipes.
Explain how ionisation of a material takes place.
When an atom gains or loses an electron it becomes ionised.
Define the term ‘half life’
Half life is the time taken for half of the radioactive nuclei in a sample to decay.
Or the time for the activity to halve.
How many radiactive nuclei remain in a sample after 2 half lives?
A quarter will be left after 2 half-lives.
(Half after one half life, half of that after 2, etc)
Describe what happens in beta decay.
A neutron breaks up into a proton and a high speed electron during beta decay.
Explain why the emission of a gamma ray does not change the element.
In gamma decay the nucleus emits a high frequency electromagnetic wave. This gamma ray has no mass and no charge and so it has no effect on the mass number or atomic number of the nucleus.
Describe how radiation may be used to detect a leak in a pipe.
A source of gamma radiation is mixed into a fluid flowing through a pipe. A worker can then detect the radiation at the surface. If there is a blockage or a leak the activity detected after the blockage will fall. This alllows the worker on the surface to pinpoint where to dig.
It has to be gamma as alpha and beta are not penetrating enough.
Describe how x-rays are produced.
They are produced by firing high-speed electrons at angled metal targets inside the x-ray machine. When the electrons smash into the plate, electrons are emitted.
Explain why a radiographer leaves a room when x-rays are taken.
To reduce their exposure time to the x-rays
Describe how a radioactive tracer might be used to diagnose a problem with a patients digestive system.
A radioactive sample is either injected or eaten by the patient. The gamma rays travel out of the body and the level of radiation is picked up by a machine and converted into a picture.
Describe how nuclear reactors generate electricity?
Nuclear reactors use uranium which is split into 2 smaller nuclei when it absorbs an extra neutron. 2 more neutrons are released in the process and they go on to cause more uranium atoms to be split. This process is called nuclear fission.
Explain how a chain reaction is controlled inside a nuclear reactor.
Control rods are raised and lowered and they absorb the excess neutrons so slowing the reaction down.
What are control rods made from?
Control rods are made from boron or cadmium.
In nuclear fusion, two small atoms of hydrogen fuse together to form what?
Fusing hydrogen creates helium.
Briefly describe how scientists can use radiactivity to date rocks.
Scientists study the ratio of uranium atoms to lead atoms. As a rock ages the uranium inside it decays and eventually turns to lead. The older the rock the lower the ratio of uranium to lead.
Explain what is meant by radiocarbon dating?
Radiocarbon dating is used to date things that were once living.
This works because living things have radioactive Carbon 14 in them which decays once they die. The less C 14 in a smple, the older it is.
