P13 Electromagnetic waves

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  • Created by: wolf.dz7
  • Created on: 27-02-18 17:38
What are electromagnetic waves?
Electric and magnetic disturbances - they are able to travel through a vacuum
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Are electromagnetic waves transverse or longitudinal, or can they be either?
All electromagnetic waves are transverse (the direction of vibration is perpendicular to the direction of movement)
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Can electromagnetic waves travel through vacuums?
Yes
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Do all electromagnetic waves have the same wavelength?
No
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Do all electromagnetic waves have the same frequency?
No
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How are different waves in the electromagnetic spectrum grouped?
According to their wavelength and frequency
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What are all of the waves in the electromagnetic spectrum (in order)?
Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays
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How are the types of electromagnetic waves in the electromagnetic spectrum ordered?
In decreasing wavelength and increasing frequency and energy
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Are all electromagnetic waves reflected, absorbed and transmitted?
Yes
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Are all electromagnetic waves reflected, absorbed and transmitted in the same way?
No - different wavelengths of electromagnetic radiation are reflected, absorbed or transmitted differently by different substances and different types of surface
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The higher the frequency of the wave, the ____ energy it transfers
more
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What is wave speed?
The speed a wave travels
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Do all electromagnetic waves have the same wave speed?
Yes
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What is the wave speed of electromagnetic waves when travelling through a vacuum?
300 million (300,000,000)m/s or 3x10⁸
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What equation can be used to work out wave speed?
wave speed (v) = frequency (f) x wavelength (λ)
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How can the equation v = fλ be rearranged?
f = v/λ or λ = v/f
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Which part of the electromagnetic spectrum transfers the most energy?
Gamma rays
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Which part of the electromagnetic spectrum has the longest wavelength?
Radio waves
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What is visible light?
The part of the electromagnetic spectrum that can be detected by the human eye
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How are different colours perceived?
Different ranges of wavelengths display different colours
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Which colour has the largest wavelength and which has the smallest?
Red has the largest, violet has the smallest
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Which colour has the largest frequency and which has the smallest?
Violet has the largest, red has the smallest
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What is white light?
White light is how a mixture of all the colours is percieved
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What type of objects emit infrared radiation (IR)?
All objects emit IR
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The hotter the object, the ____ infrared radiation it emits.
more
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What are some uses of IR?
Remote controls for devices such as TV and DVD players, special cameras which allow visibility in the darkness, and they can be transmitted along optical fibres
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What are some uses of microwaves?
Cooking/heating food in microwave ovens, communications
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Explain microwaves' use in communications.
Microwave transmitters produce wavelengths that are able to pass through the atmosphere which are used to send signals to and from satellites for TV programmes and mobile phones
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How can radio waves be used?
To transmit radio and television programmes
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How can radio waves and microwaves be harmful to humans?
They can penetrate the skin and are absorbed by body tissue, causing internal heating which could cause damage
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How can infrared radiation be harmful to humans?
It is absorbed by the skin and too much will cause you to get burnt
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How can visible light be harmful to humans?
Too much can cause damage to the eyes
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How can you investigate the absorption and emission of infrared radiation? (part 1)
Take two identical cans, one with a light shiny surface and one with a matt black surface. Fill each can with the same volume of hot water at the same temperature and leave them for the same length of time. Measure the temperature in each can.
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How can you investigate the absorption and emission of infrared radiation? (part 2)
The surface of the can with the lower temperature will be the best emitter of infrared radiation. Then, fill each can with the same volume of cold water at the same temperature. Place both cans in the sunlight for the same amount of time.
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How can you investigate the absorption and emission of infrared radiation? (part 3)
Measure the temperature of both cans. The can with the higher temperature will have the surface that is the best absorber of infrared radiation.
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What are carrier waves?
Waves used to carry any type of signal
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What is the use of the different bands in the radio and microwave spectrum?
The different bands are used for different communications purposes
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Why are the different bands in the radio and microwave spectrum used for different communications purposes?
The shorter the wavelength of the waves: the more information they carry; the shorter their range; the less they spread out
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Why are microwaves used for used for satellite phone and TV signals (rather than radio waves)?
They can travel between satellites in space and the Earth
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How do some scientists think that radiation from mobile phones can be harmful?
They think the radiation may affect the brain, especially in children, but further research is needed to evaluate this claim
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What is an optical fibre?
A very thin, transparent fibre, used to transmit communication signals by visible light and infrared radiation
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Why can optical fibres containing visible light and infrared radiation be useful in communications?
They carry much more information than radio or microwave transmissions and are more secure because the waves stay in the fibre
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Why do infrared and visible light transmissions carry more information than radio or microwave transmissions?
They have shorter wavelengths than radio waves and microwaves
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How to signals in radio stations work? (part 1)
A microphone produces an audio signal when sound waves reach it which is used to modulate (vary the frequency of) carrier waves. These modulated carrier waves are supplied to the transmitter aerial, which emits radio waves that carry the audio signal
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How to signals in radio stations work? (part 2)
When the radio waves are absorbed by the receiver aerial, they induce an alternating current, which causes oscillations in the receiver with the same frequency as the frequency of the radio waves.
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How to signals in radio stations work? (part 3)
The receiver circuit separates the audio signal from the carrier waves. The audio signal is supplied to a loudspeaker, which emits sound waves.
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How can ultraviolet light (UV) be used?
For security marking and in sunbeds
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How can UV be harmful to humans?
It can cause sunburn and skin cancer and can damage the eyes
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How can X-rays be used?
To create images of bones and teeth to check for fractures and dental problems, to detect cracks in metal objects and to destroy tumours at or near the body surface
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How can gamma rays be used?
To kill harmful bacteria in foods to prevent food poisoning, to sterilise surgical instruments and to kill cancer cells
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What is ionisation and how does it link to the radiation of electromagnetic waves?
Ionisation is when atoms become charged by losing or gaining electrons - when gamma rays and X-rays pass through substances, they knock electrons out of the atoms in the substance, leaving the atoms with a positive charge
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How can ionisation from X-rays and gamma rays be harmful to living organisms?
Ionisation kills or damages living cells - it can cause cancer or damage to important tissues in the body
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What material is best at absorbing X-rays and gamma rays?
Lead
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How can lead be used for protection against X-rays and gamma rays?
People who work with these types of radiation may wear lead aprons or stay behind lead screens
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Why do people working with ionising radiation wear a film badge?
The radiation exposes the film in the badge so the worker's exposure can be monitored
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Which parts of the body absorb X-rays and which let the X-rays pass through?
X-rays mostly pass through soft tissue, but are absorbed by bones and teeth
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How can organs be made visible on X-ray images?
Some organs in the body that are made up of soft tissue can be filled with a contrast medium that absorbs X-rays, so the organ can be seen on an X-ray image
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What is radiation dose?
The total amount of ionizing radiation absorbed by material or tissue
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Other cards in this set

Card 2

Front

Are electromagnetic waves transverse or longitudinal, or can they be either?

Back

All electromagnetic waves are transverse (the direction of vibration is perpendicular to the direction of movement)

Card 3

Front

Can electromagnetic waves travel through vacuums?

Back

Preview of the front of card 3

Card 4

Front

Do all electromagnetic waves have the same wavelength?

Back

Preview of the front of card 4

Card 5

Front

Do all electromagnetic waves have the same frequency?

Back

Preview of the front of card 5
View more cards

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