P12 Flashcards
Order of the elctromagnetic spectrum left to right and frquency order
Radio waves, microwaves, infrared radiation visible light ultraviolet x-rays and gamma rays low frequency to high
Radio waves have wave lengths up to
10km
Wavelengths gamma and x rays
10 to the -15m
Visible light wave length
400 to 700nm
All electromagnetic waves travel at this speed in space or a vacuum
3.0 x 10 to the 8 m/s
Wave speed formula
Wave speed = frequency x wavelenght
What is lwhite light
Light from ordinary lightsand the sun
Wavelength increases from ? To ?
Violet to red
How can you seperate white light into different colours
With a glass prism
How does a film camera work?
The light is focused by the camera lens on to a light-sensitive film. The film then needs to be developed to see the image of the objects that were photographed.
How does a digital camera work?
The light is focused by the lens on to a sensor. This is made up of light sensitive cells or pixels. Each pixel gives dot of the image, The image is stored electronically on a mermory card.
What emits infrared radiation
All objects
How does temperature affect infrared radiation?
The hotter an object is, the more infrared radiation there is emitted.
How does infrared radiation affect the body?
The radiation is absorbed by the skin. It can damage burn or kill skin cells because it heats up the cells.
Uses of infrared?
Optical fibres in communciation systems use this because infrared is absorbed less than visible light in glass fibres.
Remote control handsets for Tv and video equipment transmit signals carried by infrared because infrared pulses easily produced and detected electrically.
Infrared scannners detect infrared emmited from hot spots onthe body indictatong unhealthy tissue.
Infrared cameras can see people and animals in the dark
To heat objects quickly electric heaters heat rooms quickly
Electric cookers with halogen hobs
Microwaves uses
Communications like satellite Tv because they can pass through the atmosphere and reach satellites above the earth. Also can carry mobile phone signals.
Microwave ovens which heat food faster because they (microwaves) penetrate into food and are abosrbed by water molecules in the food,
Radio wave frequency range
300,000hz to 3000 million hz
Radio wave uses?
Carry radio, tv and mobile phone signals, and can also connect a computer to other devices like a printer or a computer mouse like with bluetooth.
Microwaves and radio waves dangers
Can oenetrate oeople’s bodies and can heat the internal parts of the body
What are carrier waves
Waves used to carry any type of signal
The shorter the wave length of the waves
The more information they carry
The shorter their range
The less they spread out
Microwaves and radiowaves uses in communications
Microwaves used for sat phone and sat tv and tv broadcasting. Because they can travel between satelites in space and the ground and spread out less so signal doesn’t weaken much.
Radiowaves of less than 1 metre used for tv broad from tv masts because can carry more information than longer ones
From 1m to 100m used by local radio stations and 999 because limited to areas aroud the transmitter
Greater than 100 m used for national and international radio stations because long range
Radio waves phone danger
May affect braina nd children have thinner sculls
What are optical fibres
Very thin glass fibres
What are optical fibres used for
Transmit signals carried by light or infrared. The light rays can not escape from the fibre. Wehn they reach the surface of the fibre, they are reflected back in to it.
Optical fibres compared to radio waves and micro waves
Optical fibres carry much more information as light has much shorter wavelength than radio waves
Optical fibres more secure as the signals stay in the fibre
Uses pf uv waves
Posters and glow in dark ink. And security marker pens
Uv light dangers
Harmful to eyes and can cause blindness. Uv waves carry more energy than visible light waves.
Harmful to skin . Can age skin earlier.
Use sun cream don’t go over the recommended time in a sunbed and wear goggles.
Xrays and gamma do they pass through objects
Pass thorugh theme if they are not too dense and thick but a thick plate mof lead will stop them.
X rays and gamma similarities?
Are short wavelength
Carry much more energy per sec than longer wavelength waves.
Xray and gamma difs
X rays produced when electrons or other partciles moving at high speeds are stopped. x ray tubes used to produce x rays.
Gamma rays prodcued by radioactive substances when unstable nuclei release energy
Gamma rays have shorter wavelength so they can penertrate more substances than x rays
X ray uses
Medical scanning (to create images) of brokenlimbs
Detect internal cracks in metal objects
Uses of gamma rays
Kill harmful bacteria in food like salmonella.
Sterilise medical instruments.
Gamma ray thrapy used to destroy cancerous tumours.
Narrow beam used from radioactive source cobalt 60 and is directed at the tumour and is aimed at tumour from different directions.
X ray and gamma dangers
When they pass through subs they can knock electrons out of atoms so atoms become charged and this is called ionisation. So x rays and gamma are ionisingradiation. If ionisation happens to a living cell can damage or kill the cell. Exposure tot toom many can cause cancer. Hugn doeses kill livimg. cellsa nd low doese cause gene mutation and cacnerous growth. Wokrers must wear a film badge that shows that it is over exposed to ionising radiation so they can stop workeing with equipment
X -ray proccess
X ray tube switched on and the rays pass through the body part
Pass soft tissue but absorbed by bones teeth and metal objects that arent too thin
The parts of the film that the x rays reacn become darker so bones appear lighter.
An organ of soft tissue can be filled with comtrast medium that absorbs x rays easily which enables internal structures in organ to show up. Barium meal given to people before stomach x ray as barium compound good absorber of x rays. Ccd sensors convert x rays to light adn x ray digital iage shown
Lead plates role in x rays.
Between tube and parient to stop x rays reaching other patts of body. Lead is a good absrober of x rays
Three types of radiation fromr adioactive subs
Gamma
Alpha
Beta
What is radiation dose
Measure of the damage done to their body by ionising radiation
What three things does radiation dose depend on
Type of radiation
How long the exposure is
Energy persecond absorbed by the body from radiation
What is x ray therapy?
Doctors use this to destroy cancerous tumours in th ebody. Shorter in wavelength than waves isedfor imaging
