Ch - 15 (Electromagnetic Spectrum) Flashcards
What are the electromagnetic spectrum waves?
- Radio waves
- Microwaves
- Infrared
- Visible
- Ultraviolet
- X rays
- Gamma rays
From longest wavelength (lowest frequency) to smalles wavelength and highest frequency.
What’s re the effects of radiation with High energy?
- Highly ionising
- Harmful toc ells and tissue causing cancer.
What is the effect of radiation with lower energy?
- Useful for communications
- less harmful to humans
Define electromagnetic waves.
Transverse waves that transfer energy from the source of the waves to an absorber
What are common properties of all waves?
- They are all transverse
- they can travel through vacuum
- They all travel at same speed (3.0 x 10^8 m/s)
What is radio used for?
Communication (radio or tv)
what is the use of microwave?
- Heating food
- communication (WiFi, mobile phones, satellites)
What is the use of infrared waves?
- remote controls
-fibre optic communications - heating or cooking things
- electrical heaters
What is the use of visible light?
- seeing and taking photo
- fibre optic communication
What is the use of ultraviolet rays?
- Security marking
- Fluorescents bulbs
- Getting a suntan
What is the use of x-rays?
- X - Ray images (medicine)
- Security checking
What is the use of gamma rays?
Sterilizing medical instruments
Treating cancer
What is the main use of radio waves?
Wireless communication and heating (very High intensities)
What is the main use of infrared radiation?
- security cameras (Used to illuminate an area without being seen, which is seen by detecting cameras)
- Fiber optical cables
- remote controls
- emitted by warm objects
What is the range of visible light wavelength that human can detect?
from 750 nanometers (red light) up to 380 nanometers (Violet light)
What is ultraviolet responsible for?
- giving a sun tan
- When exposed, they absorb and re-emit it as visible light (also called fluorescence)
What is fluorescence used for?
Used to make secretly mark things using special ink.
Light bulbs also use it
What is the main use of X - rays?
- Able go pass through most body tissues but are absorbed by denser parts of body (bone)
- bones absorb the x - rays, leaving a shadow which can be seen when using a special x - Ray detector or photographic film.
What is the main use of gamma rays?
- Kill living cells and tissues
- effective at destroying cancerous cells
- sterilize food and medical equipment
what EM waves are ionising?
- Ultraviolet
- x rays
- gamma rays
what happens as the frequency of EM waves increases?
Energy increases
how does the danger associated with EM waves increase?
- With frequency
- Shorter the wavelength, the more ionizing the radiation
- intensity of wave also plays a role
What is the danger of radio waves?
Nothing
What is the danger of microwave?
Possible heat damage to internal organs
What is the danger of infrared?
Skin burns
What damage is caused by visible light?
Bright light can cause eye damage
What is the danger of ultraviolet?
- Eye damage
- Sunburn
- Skin cancer
What is the danger of X - rays?
- Kills cells
- Mutation
- Cancer
What is the danger of Gamma rays?
- Kills cells
- Mutations
- cancer
Why does microwaves cause internal heating?
Absorbed by water molecules
What does ultraviolet result in?
Premature ageing, ionizing
What do X - rays and gamma rays do?
- penetrate through body and cause internal damage.
- cause mutation of genes and cause cancer
What’s re geostationary satellites used for?
Communicating information
What is the use of geostationary satellites or low orbit satellites?
- above earth’s equator
- orbit the satellites in 24 hrs
- at a height of 36, 000 km higher than polar
- used for radio and telecommunication
what is the characteristic of polar or low orbits satellites?
- orbit around North and south poles
- 200km above sea level
What are the sues of polar satellites or low orbits?
- monitoring weather
- much shorter time delay
- signals and images are much clearer
- limited use in any one orbit
What systems rely on long wave electromagnetic radiation?
- mobile phones, wireless internet & satellite television (using microwave)
- Bluetooth, terrestrial television signals & local radio stations (using radio waves)
- optical fibers (using visble or infrared waves)
What distance do radio waves transmit?
- Short distances
- Terrestrial (local) television signals, radio stations transmissions
What wavelength are radio station signals transmitted at?
- longer wavelength than terrestrial television signals
In hilly areas does it receive terrestrial television signals or radio signals?
Radio signals because they are more prone to diffraction around the hills
Does Bluetooth use waves or wires?
Radio waves, over short distances.
What wavelength do Bluetooth signals have?
- shorter wavelength
- enables High rates of data transmission, but can only be used for over short distances.
- they can pass through walls but signals get weakens
What signals can microwave transmit?
- large distances
- used to send signals to and from satellites
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What properties must the microwave have when transmitted from a dish?
- wavelength must be small compared to dish diameter to reduce diffraction
- dish must be made of metal because metal reflects microwaves well.
Why do mobile phones and wireless internet use microwaves?
They are not refracted, reflected or absorbed by the atmosphere or ionosphere.
Which EM wave (s) do optical fibers use?
- visible light or infrared
Why do optical fibres use visible light and infrared?
- Glass is transparent to viable and infra
- visible light have short wavelength, infrared can carry High rates of data due to high frequency.
What are the 2 types of signals?
Analogue
Digital
Define analogues signals.
Vary continuously - they can take any value
Define digital signals
- can only take one of two (discrete) states
- 1s and 0s
- High and lows
- On.s and off’s
How are signals before and after?
Before transmission: Analogue to digital
After transmission: Digital to analogue
What does analogue signal consist of?
Varying frequencies or amplitude.
Ex - analogue technology include telephone transmission and some broadcasting.
What are the advantages of digital signal?
- signal can be regenerated so there is minimal noise
- accurate signal, range of data signals is larger (they cover longer distances)
- increased rate of transmission of data
- extra data can be added to check for errors.
