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Physics IV > Electromagnetic Spectrum > Flashcards

Electromagnetic Spectrum Flashcards

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1
Q

what are electromagnetic waves

A

electromagnetic waves are electric and magnetic disturbances that transfer energy (not matter) from a source to an absorber

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2
Q

what speed does all electromagnetic waves travel at?

A

3 x 10^8 m/s

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3
Q

what is the equation of wave speed, frequency and wavelength

A

wave speed (m/s) = Frequency (Hz) x Wavelength (m)

v = f x λ

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4
Q

what order does the electromagnetic spectrum go in from the longest wavelength to the shortest

A

Radio, Microwave, Infrared, Visible light, Ultra- Violet, X-rays, Gamma rays

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5
Q

Are EM waves transverse or longitudinal

A

Transverse

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6
Q

Does energy increase or decrease from radio to gamma waves

A

Energy increases

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7
Q

Does the frequency increase towards Gamma or radio

A

Increase frequency towards gamma

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8
Q

Is wavelength larger at microwave or gamma

A
  • Wavelength larger towards radio
  • small wavelength towards Gamma
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9
Q

There is a large range of frequencies because EM waves are generated by …….

A
  • a variety of changes in atoms and their nuclei e.g. change in the nucleus of an atom creates gamma rays
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10
Q

White light contains what colours?

A

contains all the colours of the spectrum

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11
Q

what colour has the shortest and longest wavelength

A

Shortest: Violet
Longest: Red

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12
Q

What are EM waves made up of?

A

oscillating electric and magnetic fields

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13
Q

How are EM waves produced?

A
  • Alternating currents (AC) are made up of oscillating charges.
  • As the charges oscillate, they produce oscillating electric and magnetic fields, i.e. electromagnetic waves.
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14
Q

Radio waves are EM radiation with wavelengths longer than about …… cm

A

10

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15
Q

How are long- wave radios used for communication?

A
  • 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
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16
Q

What is the wavelength of long-wave radios

A

1 - 10km

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17
Q

What is the wavelength of short-wave radio signals

A

10-100m

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18
Q

How are short- wave radio signals used for communication?

A
  • can be received* at long distances from the transmitter
  • they are reflected from the ionosphere - electrically charged layer in the Earths upper atmosphere
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19
Q

Uses of radio waves

A
  • radio player
  • Bluetooth
  • Broadcasting TV
20
Q

Does Bluetooth use long or short wave radio signals

A

Short-wave
- to send data over short distances between wireless devices*

21
Q

Does TV and FM radio use long or short wave radio signals and why?

A

-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

22
Q

Uses of Infrared:

A
  • infrared cameras
  • Remote controls
  • Electrical heaters
  • Ovens
23
Q

How and what are infrared imaging used for?

A
  • 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
24
Q

Absorbing Infrared radiation causes objects to get ……

A

hotter

25
Q

How to Electrical heaters work ?

A
  • 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
26
Q

Energy is transferred by the ……. Waves to the …… of the objects, causing their …… to …….

A

Infrared
Thermal energy stores
Temperature
Increase

27
Q

Uses for Microwaves:

A
  • microwave ovens
  • mobile phones
  • satellite communication
28
Q

Why are microwaves the best for communicating satellite signals

A
  • pass easily through Earth’s watery atmosphere
  • spread out less than radio waves, signal doesn’t weaken as much
29
Q

How is satellite TV signals transmitted?

A
  • 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.
30
Q

How do Microwave ovens work?

A
  • 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.
31
Q

Uses of Visible light:

A
  • Optical Fibres
  • Cameras
  • Endoscopes
  • Torches
32
Q

What are optical fibres

A
  • *thin glass** or plastic fibres that can carry data over long distances as pulses of visible light
33
Q

How to optical fibres work/

A
  • reflection
  • light rays bounce back and forth until end of fibre
  • light is not easily absorbed or scattered as it travels along a fibre
34
Q

Radio waves of different frequencies are used for different purposes because the wavelength (and so the frequency) of waves affects:

A
  • how far they can travel
  • how much they spread
  • how much information they
    can carry.
35
Q

Uses of Ultraviolet

A
  • security pens
  • bank note identification
  • UV tanning
36
Q

What is Fluorescence

A
  • property of certain chemicals, wher UV radiation is absorbed and **visible light ** is emitted
37
Q

Waves can transfer …. And ……

A

Energy, information

38
Q

What are Carrier waves and examples

A

Waves that carry information. Do this by varying their amplitude
- radio waves
- microwaves
- infrared radiation
- visible light

39
Q

Why do shorter wavelengths carry more information and what are the disadvantages

A
  • shorter wavelength = higher frequency so more waves arrive quicker
  • more information transferred
  • Disadvantage: range is less, due to increase absorption by the atmosphere
40
Q

Uses of gamma rays:

A
  • killing harmful bacteria in food or surgical equipment
  • cancer treatment
41
Q

Uses of X-rays

A
  • X-ray imaging / Radiographs
42
Q

why does ionisation occur in X-rays and Gamma rays

A
  • 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.
43
Q

What can X-rays be blocked by

A
  • bones
  • teeth
  • metal inside body
44
Q

How can we X-rays soft tissue organs?

A
  • filling organs with a contrast medium
  • absorbs X-rays
  • enables internal surfaces in the organ to be seen on radiograph
45
Q

Radiation does is a measurement of what

A

The damage done to their body by ionising radiation

46
Q

What 3 things does the radiation does depend on:

A
  • radiation types
  • time exposed
  • energy per second absorbed (surface area, concentration )
47
Q

Dangers of UV radiation

A
  • damage surface cells
  • can lead to sunburn
  • skin to age prematurely
  • blindness
  • increase risk of skin cancer

Physics IV (16 decks)

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