alpha ionising. how an ‘ionisation smoke alarm’ works a source of alpha radiation is placed in...

Alpha

Ionising

How an ‘Ionisation Smoke Alarm’ works

A source of alpha radiation is placed in the detector close to two electrodes

The source causes the air to ionise, and a current flows

If there is a fire then smoke will absorb the most of the ions – the current falls

The siren will sound when the detector current falls .

Paper thickness control mill

A paper mill regulates the thickness of the paper by using a alpha source.

Beta

Ionising

Hydraulicram

detector

Aluminium thickness control mill

Electronic instructions to adjust rollers.

Beta Source

A radioactive source is on one side of the material and a detector on the other.

If too much beta radiation is getting through, then the material is too thin and the rollers open up a bit to make the material thicker.

Gamma

Ionising

Detecting leaking underground pipes

The isotope must have a short half life so the material does not become a long term problem.

The isotope must have a short half life so the material does not become a long term problem.

The radioactive isotope must be a gamma emitter so that it can be detected through the metal and the earth where the pipe leaks. Alpha and beta rays would be blocked by the metal and the earth.

The radioactive isotope must be a gamma emitter so that it can be detected through the metal and the earth where the pipe leaks. Alpha and beta rays would be blocked by the metal and the earth.

Gamma radiation can be used to sterilise food or medical instruments. The gamma rays pass through the object, killing any microbes as they pass through.

Sterilisation

Radioactive Tracers

A gamma camera detects the radiation coming from the patient and produces an image of where the radioactivity is in the body.

Doctors may use radioactive chemicals called tracers for medical imaging. Certain chemicals concentrate in different damaged or diseased parts of the body, and the radiation concentrates with it. Radiation detectors placed outside the body detect the radiation emitted and, with the aid of computers, build up an image of the inside of the body.When a radioactive chemical is used in this way it is not normally harmful, because:it has a short half-life and so decays before it can do much damage Emitters of gamma radiation are used because gamma radiation can penetrate through the body.

Radiotherapy Radiotherapy The tumour is exposed to gamma radiation at

different angles.

However, levels have to be carefully monitored so that healthy cells are not damaged as well.

This gives normal cells a low dose of radiation, while the tumour receives a high dose.

In some patients radiation treatment may not be able to destroy the cancer. Sometimes it is used only to reduce suffering (palliative care).

tumour

Rotating gamma source

X-rays

Ionising

Radiotherapy Radiotherapy The tumour is exposed to X-rays radiation at

different angles.

However, levels have to be carefully monitored so that healthy cells are not damaged as well.

This gives normal cells a low dose of radiation, while the tumour receives a high dose.

In some patients radiation treatment may not be able to destroy the cancer. Sometimes it is used only to reduce suffering (palliative care).

tumour

Rotating X-ray source

A CT (computer tomography) scan can produce a 3D computer-generated image of soft tissue.

A patient undergoing a CT scan. On the computer are image slices of her abdomen.

CT scan X-ray diagnosis

Mammogram

An X-ray is taken to check for breast cancer

X-rays - airport security

X-ray photography

X-rays can penetrate the body. The photographic film is turned from white to black by X-rays, so the more X-rays that are absorbed by an area of the body, the whiter that area will appear. This is why bones appear white on X-ray photographs.

Ultra-violet

Ionising

Skin clinics - skin analysis

UV imaging technique

Detecting forged bank notes

U.V. LIGHT: A genuine bank note should not fluoresce right across the banknote. Many banknotes have fluorescent marking in the note. When they are held under the U.V. light the marking will appear (only the design should fluoresce when passed under the U.V. light).

Ultraviolet - Sunbeds

Darkening of the skin is caused by an increased release of the pigment melanin into the skin's cells after exposure to ultraviolet radiation. Melanin is produced by cells called melanocytes and protects the body from direct and indirect DNA damage absorbing an excess of solar radiation, which can otherwise be harmful.

Radio waves

Non-ionising

Broadcasting and CommunicationBroadcasting and Communication

Radio waves are emitted by a radio or television transmitting aerial and picked up by a receiving aerial.

Transmitter tower

Radio waves are used mainly for broadcasting and communication purposes, and can send information over very long distances.

The waves reach a radio or television aerial

Microwaves

Non-ionising

Microwaves - Mobile Phones

Microwaves are used to transmit mobile phone calls.

MeteorologyEver noticed how your mobile phone can lose reception during heavy rain?

Microwaves are absorbed by water.

To make a microwave image, emitters on earth send microwaves to satellites in space.

Detectors on the satellite measure any decrease in the strength or amplitude of the microwaves due to heavy rainfall or cloud.

The decrease is colour coded and shows as rain cloud on computer

Microwave OvensMicrowave Ovens

The microwaves penetrate the food and are absorbed by the water molecules inside the food which then vibrate vigorously.

Infra-red

Non-ionising

Seeing invisible infra-red waves!

You need:Infra-red remote controlMobile phone with camera facility

Remote Controls

Remote control handsets all use infra red radiation.

On each satellite there are two types of sensors. One is a visible light sensor called the "imager," which works like a camera in space and helps gather information on cloud movements and patterns. This sensor can only be used during daylight hours, since it works by capturing reflected light to create images.

The second sensor is called the "sounder." It's an infrared sensor that reads temperatures. The higher the temperature of the object, the more energy it emits. This sensor allows satellites to measure the amount of energy radiated by Earth's surface, clouds, oceans, air, and so on. Infrared sensors can be used at night—a helpful feature for forecasters, considering that the imager can only pick up data during daylight hours.

Weather satellites

Infra - red

• Heat radiation is absorbed by the molecules in the food causing them to vibrate.

• Heat energy is then passed from one molecule to another by a process called conduction

Cooking with waves

• Eventually heat energy spreads throughout the food item

Infra-red cameras are used to study heat loss from buildings and guide advice on insulation requirements.

Thermograms

Doctors can use thermal imaging cameras to assess the state of the body e.g. cancer tissues are hotter than normal body tissues.

Detecting metal fatigue in aeroplanes

Infra red radiation can be used for heat treatment and to keep young chicks warm. However, over exposure to infra red radiation can cause damage to cells and burn the skin.

Relieves back pains

Visible light

Non-ionising

Fibre optics (fibre optic communications). The transmission of information by the passage of light through flexible, glass fibres. Electrical impulses are converted into light which is then transmitted through the optical fibre. The light is then re-converted into electrical impulses at its destination.

The military use lasers for guiding missiles.

Visible light from lasers is used to read CD ROMs and DVDs in computers and multimedia entertainment.

Lasers are used in cutting machines

Lasers are used to read bar codes Lasers

Entertainment

Reflectors for safety

Reflectors are really strips of material with small prisms embedded in their surface. Each prism performs total internal reflection twice on the incident light.

Total Internal Reflection - Catseye

Uses of Light - Safety Clothing

Reflective clothing

EndoscopeEndoscope

An endoscope allows doctors to see inside a patient’s body, either while they are carrying out an operation, or diagnosing a problem.