Electromagnetic Spectrum Flashcards
what are electromagnetic waves
electromagnetic waves are electric and magnetic disturbances that transfer energy (not matter) from a source to an absorber
what speed does all electromagnetic waves travel at?
3 x 10^8 m/s
what is the equation of wave speed, frequency and wavelength
wave speed (m/s) = Frequency (Hz) x Wavelength (m)
v = f x λ
what order does the electromagnetic spectrum go in from the longest wavelength to the shortest
Radio, Microwave, Infrared, Visible light, Ultra- Violet, X-rays, Gamma rays
Are EM waves transverse or longitudinal
Transverse
Does energy increase or decrease from radio to gamma waves
Energy increases
Does the frequency increase towards Gamma or radio
Increase frequency towards gamma
Is wavelength larger at microwave or gamma
- Wavelength larger towards radio
- small wavelength towards Gamma
There is a large range of frequencies because EM waves are generated by …….
- a variety of changes in atoms and their nuclei e.g. change in the nucleus of an atom creates gamma rays
White light contains what colours?
contains all the colours of the spectrum
what colour has the shortest and longest wavelength
Shortest: Violet
Longest: Red
What are EM waves made up of?
oscillating electric and magnetic fields
How are EM waves produced?
- Alternating currents (AC) are made up of oscillating charges.
- As the charges oscillate, they produce oscillating electric and magnetic fields, i.e. electromagnetic waves.
Radio waves are EM radiation with wavelengths longer than about …… cm
10
How are long- wave radios used for communication?
- long wavelengths can diffract(bend) around the curved surfaces on the Earth
- can diffract around hills, into tunnels
- makes it possible for radio waves to be received even if the receiver isn’t in the line of sight of the transmitter
What is the wavelength of long-wave radios
1 - 10km
What is the wavelength of short-wave radio signals
10-100m
How are short- wave radio signals used for communication?
- can be received* at long distances from the transmitter
- they are reflected from the ionosphere - electrically charged layer in the Earths upper atmosphere
Uses of radio waves
- radio player
- Bluetooth
- Broadcasting TV
Does Bluetooth use long or short wave radio signals
Short-wave
- to send data over short distances between wireless devices*
Does TV and FM radio use long or short wave radio signals and why?
-TV and FM transmissions have very short wavelengths
-need to transfer a lot of information
- to get reception must in direct sight of transmitter
- signal doesn’t bend or travel far through buildings
Uses of Infrared:
- infrared cameras
- Remote controls
- Electrical heaters
- Ovens
How and what are infrared imaging used for?
- to detect infrared radiation
- ** monitor temperature**
- camera detects IR temperature and turns it into an electrical signal
- displayed on the screen as a picture
- hotter the object is, brighter it appears
Absorbing Infrared radiation causes objects to get ……
hotter
How to Electrical heaters work ?
- contain long piece of wire that hearts up when a current flows through
-wire then emits lots of infrared radiation(and a little visible light- glows ) - emitted IR absorbed by objects and air in surroundings
Energy is transferred by the ……. Waves to the …… of the objects, causing their …… to …….
Infrared
Thermal energy stores
Temperature
Increase
Uses for Microwaves:
- microwave ovens
- mobile phones
- satellite communication
Why are microwaves the best for communicating satellite signals
- pass easily through Earth’s watery atmosphere
- spread out less than radio waves, signal doesn’t weaken as much
How is satellite TV signals transmitted?
- signal from transmitter, transmitted into space
- signal picked up by satellite receiver dish ORBITING thousand of km above Earth
- satellite transmits the signal back to Earth in a different direction
- it’s received by a satellite dish on the ground.
- There is a slight time delay between the signal being sent and received because of the long distance the signal has to travel.
How do Microwave ovens work?
- microwaves absorbed by water molecules in food
- microwaves penetrate up to a few centimetres into the food before being absorbed and transferring the energy they carry to the water molecules in the food, causing the water to heat up.
- water molecules then transfer energy to the rest of the molecules in the food by heating - which guickly cooks the food.
Uses of Visible light:
- Optical Fibres
- Cameras
- Endoscopes
- Torches
What are optical fibres
- *thin glass** or plastic fibres that can carry data over long distances as pulses of visible light
How to optical fibres work/
- reflection
- light rays bounce back and forth until end of fibre
- light is not easily absorbed or scattered as it travels along a fibre
Radio waves of different frequencies are used for different purposes because the wavelength (and so the frequency) of waves affects:
- how far they can travel
- how much they spread
- how much information they
can carry.
Uses of Ultraviolet
- security pens
- bank note identification
- UV tanning
What is Fluorescence
- property of certain chemicals, wher UV radiation is absorbed and **visible light ** is emitted
Waves can transfer …. And ……
Energy, information
What are Carrier waves and examples
Waves that carry information. Do this by varying their amplitude
- radio waves
- microwaves
- infrared radiation
- visible light
Why do shorter wavelengths carry more information and what are the disadvantages
- shorter wavelength = higher frequency so more waves arrive quicker
- more information transferred
- Disadvantage: range is less, due to increase absorption by the atmosphere
Uses of gamma rays:
- killing harmful bacteria in food or surgical equipment
- cancer treatment
Uses of X-rays
- X-ray imaging / Radiographs
why does ionisation occur in X-rays and Gamma rays
- when x-rays or gamma rays pass through a substance
- knock electron out of their atoms in substance
- if ionisation happens to living cells it can damage cells
- Gene mutations, cell destruction, cancer.
What can X-rays be blocked by
- bones
- teeth
- metal inside body
How can we X-rays soft tissue organs?
- filling organs with a contrast medium
- absorbs X-rays
- enables internal surfaces in the organ to be seen on radiograph
Radiation does is a measurement of what
The damage done to their body by ionising radiation
What 3 things does the radiation does depend on:
- radiation types
- time exposed
- energy per second absorbed (surface area, concentration )
Dangers of UV radiation
- damage surface cells
- can lead to sunburn
- skin to age prematurely
- blindness
- increase risk of skin cancer
