P13 - Electromagnetic Waves✔️ Flashcards
Why do electromagnetic waves have different effects?
Electromagnetic waves do not transfer matter - the energy they transfer depends on the wavelength of the waves this is why waves of different wavelengths have different effects
What speed do electromagnetic waves travel at?
300 million m/s through space or in a vacuum
Equation for wave speed?
Wave speed = frequency x wavelength
Electromagnetic waves in order of increasing frequency and decreasing wavelength?
Radiowaves - microwaves - infrared radiation - visible light - unltraviolet waves - x rays and gamma rays
Why is light from ordinary lamps and from the sun called white light?
Because it contains all the colours of the visible spectrum in it
Features of infrared radiation?
-hotter an object more infrared radiation is emmited
-infrared radiation is absorbed by your skin , it can damage,burn or kill skin cells
3 uses of infared radiation?
-infrared scanners - used in medicine to detect unhealthy tissues
-see people and animials in the dark
-heat up obects quickly - electric heaters emit infared which warms rooms quick
3 features of microwaves?
-Shorter wavelength then radio waves
-used for communications for example satellite TV because they pass through the atmosphere and reach satelites above earth
-heating up food
Why are microwaves used to heat up food?
Microwave ovens heat food faster because microwaves can penetrate into food and are absorbed by the water molecules in the food
Fequency and fetaures of radiowaves?
frequencies range from about 300,000 Hz to 3000 million Hz and are used to carry tv and mobile phone signals
Why can radio and microwaves be hazardous?
They penetrate peoples bodies and can heat the internal parts of the body causing damage
Define carrier waves?
Waves used to carry any type of signal they could be radiowaves,microwavess or visible light - they do this by varying their amplitude
A shorter wavelength results in …?
-The wave carrying more information
-shorter the waves range (increasing absorption by the atmosphere)
-the less the waves spread out
3 uses of microwaves?
-satelite phone
-tv links
-satelite TV broadcasting
Why are microwaves used for satelite TV braodcasting?
Microwaves can travel between satelites in space and the ground and they spread out less than radio waves so the signal doesn’t weaken as much
Uses of radiowaves less than about 1 metre?
-TV braodcasting from TV masts - because they can carry more infromation than longer radiowaves
Uses of radiowaves about 1 to 100 metres?
-used by local radiostations and for emergency services because the range is limited to the area round the trasmitter
Uses of radiowaves greater than 100 metre?
Used by national and international radio stations because they have much longer range than shorter wavelength radio waves
How can mobile phones radiowaves be dangrous?
If the phone is very close to the your head , some scientists think the radiation might affect the brain especialy in children because they have thinner skulls then adults
What are optical fibres?
Very thin transparent fibres that are used to transmit communication signals by light and infarred radiation
Benefits of optical wires?
-carry much more information as light has a much shorter wavelength than radio waves and so can carry more impulses of waves
-optical fibres are more secure because the signals stay in the fibre
Issues with sunbeds and UV light?
Ultraviolet waves are harmful to your skin - and to much UV from the sun or from sunbeds can cause sunburn and skin cancer
Why is lead used to stop x-rays and gamma rays?
Because x-rays and gamma rays both travel straight into substances and can pass through them if the substance is not dense and thick enough so lead is often used
Similar properties between x-rays and gamma rays?
-are at the short-wavelength end of the electromagnetic spectrum
-carry more energy per second than longer-wavelength electromagnetic waves
Different properties between x-rays and gamma rays?
-x-rays are produced when electrons or other particles moving at high speeds are stopped - x-ray tubes are used to produce x-rays
-gamma rays are produced by radioactive substances when unstable nuclei release enegry
-gamma rays have shorter wavlengths than x-rays so they can penetrate more than x-rays can
2 uses of x-rays?
-used to detect internal cracks in metal objects - more dense a substance is the more x-rays it abbsorbs from an x-ray beam passing through it
-medecine ot reate images of broken limbs
2 uses of gamma rays?
-exposing food to gamma rays to kill bacteria and disease carrying organisms
-disinfecting and steralising surgical equipment to kill any bactiera
Explain how and why gamma rays are used for killing cancerous cells?
Use gamma rays to destroy cancerous tumours - narrow beam of gamma ray from a radioactive source is directed at the tumour and is aimed in a way as to not kill the healthy surrounding tissue
Define ionisation?
The process in which x-rays and gamma rays passing through substances can knock electrons out of atoms in the substance - the atoms become charged because they lose electrons
Why is ionising radiation dangrous?
ionisation to living cells can damage or kill the cell - with low doses causing gene mutation and cancerous growth
Exaplain in 3 steps how x-rays are used to identify damages to the bone ?
1)x-ray tub is switched on and x-rays pass from tube through the part of the patients body being investigated
2)x-rays pass through soft tissue and cracks in bone but are absorbed by bones so the parts of the film or detector that the x-ray reach become darker then the other parts so the bone apears lighter the surrounding tissue
3)flat-panel detector containing a CCD converts the x-rays to light - light rays then create electronic signals which are are sent to a computer to display a digital x-ray image
How can an organ or soft tissue be seen on the radiograph?
Soft tissue can be filled with a substance called a contrast medium that absorbs x-rays easily which enables the internal surface in the organ to be seen on the radiograph - patient also given a barium meal before the x-ray because it is a good absorber of x-rays
Method the stop x-rays reaching other parts of the body?
Lead plate are used between the tube and the patient
What is a flat-panel detector and how does it help display the x-ray as a digital image?
Is a small screen that contains a charge-coupled device (CCD) - the sensors in the CCD convert x-rays to light - the light rays then create electronic signals in the sensors that are sent to a computer whch displays a digital x-ray image
2 types of ioning radiation in the form of particles?
-beta
-alpha
2 types of ioning radiation in the form of waves?
-x-rays
-gamma rays
3 factors that effect radiation dose?
-type of radiation used
-how long the body is exposed to it
-the energy per second absorbed by the body from the radiation
Why are low-energy x-rays suitable for imaging?
-absorbed by bones and teeth but pass through soft tissue and gaps such as cracks in the bone
-do not carry enough energy to destroy cancerous tumours
