Transcript Uses of Ionising and Non-Ionising Radiation

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
Aluminium thickness control mill
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.
Beta Source
detector
Hydraulic
ram
Electronic instructions to adjust rollers.
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 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.
Sterilisation
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.
Radioactive Tracers
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.
A gamma camera detects the radiation coming from the patient and produces
an image of where the radioactivity is in the body.
Radiotherapy
 The tumour is exposed to gamma radiation at
different angles.
 This gives normal cells a low dose of radiation,
while the tumour receives a high dose.
 However, levels have to be carefully monitored
so that healthy cells are not damaged as well.
Rotating
gamma source
tumour
In some patients radiation treatment may not be able to destroy the cancer.
Sometimes it is used only to reduce suffering (palliative care).
X-rays
Ionising
Radiotherapy
 The tumour is exposed to X-rays radiation at
different angles.
 This gives normal cells a low dose of radiation,
while the tumour receives a high dose.
 However, levels have to be carefully monitored
so that healthy cells are not damaged as well.
Rotating X-ray
source
tumour
In some patients radiation treatment may not be able to destroy the cancer.
Sometimes it is used only to reduce suffering (palliative care).
CT scan
X-ray diagnosis
A CT (computer tomography) scan can produce a 3D computergenerated image of soft tissue.
A patient undergoing a CT scan.
On the computer are image slices
of her abdomen.
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 Communication
Radio waves are emitted by a radio or television
transmitting aerial and picked up by a receiving
aerial.
The waves reach a radio
or television aerial
Radio waves are used mainly for broadcasting and
communication purposes, and can send
information over very long distances.
Transmitter tower
Microwaves
Non-ionising
Microwaves - Mobile Phones
Microwaves are used to transmit mobile phone calls.
Meteorology
Ever 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 Ovens
The microwaves penetrate the
food and are absorbed by the
water molecules inside the food
which then vibrate vigorously.
Infra-red
Non-ionising
Remote Controls
Remote control handsets all use infra red radiation.
Seeing invisible infra-red waves!
You need:
Infra-red remote control
Mobile phone with camera facility
Weather satellites
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.
Cooking with waves
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
• Eventually heat energy spreads
throughout the food item
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 cameras are used to study heat loss from
buildings and guide advice on insulation requirements.
Relieves back pains
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.
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.
Lasers are used
to read bar codes
The military use lasers for
guiding missiles.
Lasers
Entertainment
Visible light from lasers is used to read
CD ROMs and DVDs in computers and
multimedia entertainment.
Lasers are used in cutting machines
Total Internal Reflection - Catseye
Reflectors are really strips of material with small prisms embedded
in their surface. Each prism performs total internal reflection twice
on the incident light.
Reflectors for safety
Uses of Light - Safety Clothing
Reflective clothing
Endoscope
An endoscope allows doctors to see
inside a patient’s body, either while
they are carrying out an operation,
or diagnosing a problem.