# Physics (P1) - Electromagnetic Waves

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• Created by: Roma
• Created on: 13-12-13 21:20
Electric and magnetic disturbances that travel as waves and move energy from place to place.
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What are electromagnetic waves?
Electromagnetic waves travel through space at the same speed at 300 million m/s, but have different wavelengths and frequencies.
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What is the electromagnetic spectrum?
All electromagnetic waves grouped at approximate boundaries according to their wavelength and frequency in a continuous spectrum.
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Which waves have the highest and lowest wavelengths and frequencies?
Gamma rays have the shortest wavelength and highest frequency. Radio waves have the longest wavelength and lowest frequency. The higher the frequency of the waves, the more energy it transfers.
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What is the order of the electromagnetic spectrum from highest to lowest wavelength?
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What is visible light?
The part of the electromagnetic spectrum which is detected by our eyes and can be seen as different colours and is used for photography.
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Radiation given out by all objects. The hotter the object, the more it emits. Remote controls use IR.
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What are microwaves?
Waves used in communications that are able to pass through the atmosphere. They are used to send signals to and from satellites and within mobile phone networks.
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Waves that transmit radio and TV programs and carry mobile phone signals.
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What are the potential risks of waves?
Microwave radiation and radio waves penetrate your skin and are absorbed. This can heat internal organs and damage then. IR radiation is absorbed by skin and can burn it.
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What is alternating voltage?
Alternating voltage applied to an aerial emits radio waves with the same frequency as the alternating voltage. When the waves are received they produce alternating current in the aerial with the same frequency as the radiation recieved.
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Why is the radio and microwave spectrum divided into bands?
So they can be used for different communication purposed. The shorter the wavelength, the more information they carry. They shorter their range, the less they spread out.
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How do mobile phones communicate?
With a local mobile phone mast using wavelengths between radio and microwaves.
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What are optical fibres?
Very thin glass fibres, used to transmit signals carried by visible light or infrared radiation.
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How do optical fibres work and why are they useful?
The signal travels down the fibre by repeated total internal reflection. They can carry visible light or infrared which is useful because they carry much more information and are more secure than radio waves and microwaves.
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What is the doppler the effect?
When a wave source is moving relative to an observer, the wavelength and frequency of the waves detected by the observer will not have changed from the original. y
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How does the doppler effect work and how can it be demonstrated.
To the observer, when the source moves away, the wavelength increases and the frequency decreases and vice versa . It can demonstrate sound waves - e.g. an ambulance siren has a higher pitch if it moves towards you and vice versa.
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What is red shift?
Light observed from distant galaxies move to the red end of the spectrum, meaning that frequency has decreased and wavelength has increased.
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What is the opposite of red shift?
Blue shift.
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What evidence is there to show that the universe is expanding?
The further away the galaxy, the bigger the red shift which suggest galaxies are moving away from us and the most distant galaxies are moving the fastest. All the galaxies are moving away from each other so the universe is expanding.
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What is the Big Bang Theory?
A theory to suggest that the universe started with a massive explosion at a very small initial point.
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What is cosmic microwave background radiation?
The high gamma radiation that would have been produced due to the Big Bang. It would then have become lower energy radiation and could be what we now call CMBR.
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## Other cards in this set

### Card 2

#### Front

What are electromagnetic waves?

#### Back

Electromagnetic waves travel through space at the same speed at 300 million m/s, but have different wavelengths and frequencies.

### Card 3

#### Front

What is the electromagnetic spectrum?

### Card 4

#### Front

Which waves have the highest and lowest wavelengths and frequencies?

### Card 5

#### Front

What is the order of the electromagnetic spectrum from highest to lowest wavelength?