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GCSE Physics (P1) > Electromagnetic Waves > Flashcards

Electromagnetic Waves Flashcards

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1
Q

What are electromagnetic waves and how do they transmit energy?

A

Electric and magnetic disturbances that transfer energy from one place to another

They cause oscillations in electric and magnetic fields and therefore do not require particles to transfer energy

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2
Q

Complete the sentence:

Electromagnetic waves have the same _____ but different _______ and _______.

A

Electromagnetic waves have the same speed but different wavelengths and frequencies.

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3
Q

Compare the wavelength and frequency of a gamma ray to that of a radio wave

A
  • Gamma rays have the shortest wavelength and highest frequency
  • Can have wavelengths as short as 10-15m
  • Radio waves have the longest wavelength and lowest frequency
  • Can have wavelengths of more than 10,000m
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4
Q

The electromagnetic spectrum is continuous. What does this mean?

A

The frequencies and wavelengths at the boundaries are approximate as the different parts of the spectrum are not precisely defined

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5
Q

Complete the sentence:

Different wavelengths of electromagnetic radiation are…

A

…reflected, absorbed, or transmitted differently by different substances and types of surface

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6
Q

Complete the sentence:

The higher the frequency of the electromagnetic wave…

A

…the more energy it transfers

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7
Q

What is the wave speed at which electromagnetic waves travel through space?

A

300 million m/s

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8
Q

How do we see a mixture of all the colours?

A

As white light

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9
Q

Which colour/electromagnetic wave has the longest wavelength?

A

Red

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10
Q

What type of electromagnetic wave do remote controls for TVs and CD players use?

A

Infrared radiation

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11
Q

How and why are microwaves used in communications?

A

Microwave transmitters produce wavelengths that are able to pass through the atmosphere

They are used to send signals to and from satelites and within mobile phone networks

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12
Q

What are radio waves used for?

A

To transmit radio and TV programs and to carry mobile phone signals

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13
Q

What are the dangers of radio waves and microwaves?

A

They can penetrate your skin and are absorbed by body tissue. This can heat internal organs and may damage them

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14
Q

What are the dangers of infrared radiation?

A

It is absorbed by skin. Too much will burn your skin

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15
Q

How are radio waves produced (using electricity) for use in communications?

A
  • An alternating voltage applied to an aerial emits radio waves with the same frequency as the alternating voltage
  • When the waves are recieved they produce and alternating current in the aerial with the same frequency as the radiation recieved.
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16
Q

What are ‘bands’?

A

The parts of the radio wave and microwave spectrum used for communications

Different bands are used for different communication purposes

17
Q
A
18
Q

Complete the sentence:

The shorter the wavelength of waves…

A

… the more information they can carry, the shorter their range, the less they spread out

19
Q

How do mobile phones work?

A

They communicate with a local mobile mast using wavelengths just on the border between radio waves and microwaves

They are usually referred to as microwaves

20
Q

Are mobile phones safe to use?

A

Some scientists think that the radiation from mobile phones may affect the brain, especially in children

More research is needed to evaluate whether or not this is true

21
Q

What are optical fibres and how do they work?

A
  • Very thin glass fibres
  • Used to transmit signals carried by visible light or infrared
  • The signals travel down the fibre by repeated total internal reflection
22
Q

Why are optical fibres useful in communications?

A

Because they use visible light/infrared. Tsis means they are able to carry more information and are more secure than radio/microwave trasmissions

23
Q

What is the Doppler effect?

A

It’s the apparent change in the frequency of a wave caused by relative motion between the source of the wave and the observer.

https://www.youtube.com/watch?v=Y5KaeCZ_AaY

24
Q

What happens when the wave source moves away from the observer?

A

The observed wavelength increases and the frequency decreases

25
Q

What happens when the wave source moves towards the observer?

A

The observed wavelength decreases and the frequency increases

26
Q

How can the Doppler effect be demostrated?

A

With sound waves.

For example, an ambulence siren will sound different depending on whether it’s moving towards or away from you

Towards = higher pitch, away = lower pitch

27
Q

What is red-shift?

A
  • Light observed from distant galaxies has been ‘shifted’ towards the red end of the spectrum
  • This means that the frequency has decreased and the wavelength has increased
  • The further away the galaxy, the bigger the red-shift. This suggests that distant galaxies are moving away from us and that the most distant galaxies are moving the fastest
  • This is true no matter what direction you look. All the galaxies are moving away from each other, so the whole universe is expanding from a singular point.
28
Q

What is blue-shift?

A

The reverse of red-shift.

Observed in galaxies emitting dark lines in their spectra. Would indicate that galaxies are moving towards us (but they aren’t)

29
Q

What is the Big Bang Theory?

A

The theory that the universe began as a massive explosion from a single point (singularity) and has continued expanding outwards ever since

30
Q

What is CMBR and how does it provide evidence for the Big Bang Theory?

A
  • If the universe began with a Big Bang, high energy gamma radiation would have been emitted. As the universe expanded, this would have become lower-energy radiation
  • Scientists have discovered microwaves coming from every direction in space
  • This is cosmic microwave background radiation, the radiation produced just after the Big Bang occured
  • So far, the Big Bang theory is the only way to explain the existence of CMBR

GCSE Physics (P1) (6 decks)

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