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Electromagnetic Spectrum Flashcards

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 ……

25
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
26
Energy is transferred by **the ……. Waves** to the …… of the objects, causing their …… to …….
Infrared Thermal energy stores Temperature Increase
27
Uses for Microwaves:
- microwave ovens - mobile phones - satellite communication
28
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
29
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.
30
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.
31
Uses of Visible light:
- Optical Fibres - Cameras - Endoscopes - Torches
32
What are optical fibres
- *thin glass** or **plastic fibres** that can **carry data** over **long distances** as pulses of **visible light**
33
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
34
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.
35
Uses of Ultraviolet
- security pens - bank note identification - UV tanning
36
What is Fluorescence
- property of certain chemicals, wher **UV** radiation is **absorbed** and **visible light ** is **emitted**
37
Waves can transfer …. And ……
Energy, information
38
What are Carrier waves and examples
Waves that carry **information**. Do this by **varying their amplitude** - radio waves - microwaves - infrared radiation - visible light
39
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**
40
Uses of gamma rays:
- killing harmful bacteria in food or surgical equipment - cancer treatment
41
Uses of X-rays
- X-ray imaging / Radiographs
42
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**.
43
What can X-rays be blocked by
- bones - teeth - metal inside body
44
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
45
Radiation does is a measurement of what
The **damage** done to their **body** by **ionising radiation**
46
What 3 things does the radiation does depend on:
- radiation types - time exposed - energy per second absorbed (surface area, concentration )
47
Dangers of UV radiation
- damage surface cells - can lead to **sunburn** - **skin to age prematurely** - **blindness** - **increase risk** of **skin cancer**

Physics (23 decks)

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