Electromagnetic waves

  • Created by: Sullster
  • Created on: 08-03-19 20:59

Radio waves

Radio waves have the longest wavelength in the electromagnetic spectrum. The wavelength of radio waves is larger than 10m(long and medium radio waves) can be transmitted around the earth by reflection off the ionosphere(upper atmosphere).

Wavelengths shorter than 10m can pass through the ionosphere. Since they can pass through the upper atmosphere these, 'ground waves' need to travel via several tranmitters that are all in 'line of sight' of each other. They can also be transmitted to distant satellites. 

Radio waves don't affect body health short term but can cause brain cancers in the long term. This would usually happen to more younger people as they have thinner skulls.



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Uses of radio waves

The uses of radio waves.

  • Broadcasting communications; carrying signals for radio and TV
  • Navigation and radar
  • Studying the universe: astronomy
  • satellite communication
  • Control signals: key fobs, garage doors
  • Tracking and automatic identification.
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Microwaves are just short wavelength radio waves.

Microwaves are absorbed by substances such as water. They can pass through the glass, China, paper and plastics but are reflected by metals. 

Mobile phones are portable microwave transmitters and receivers that communicate with the nearest base station. From there your voice information is relayed to the base station nearest person you are talking to. Finally, from there the signals travel the last leg to the person you are talking to through the phone.

As microwaves pass through the ionosphere, they can be used to send signals up to a satellite and relay them around the world.    

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Uses of microwaves

Some uses of microwaves

  • Communications: Mobile phones (just like TV transmitters, mobile phone signals require a good line of sight) and satellite transmissions
  • Cooking: Heating food a microwave oven.
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Anything that has a temperature above zero will emit infra-red waves. Certain sensors can detect infrared emitted by the body. Certain sensors can be used to activate security lights or burglar alarms.

We as human beings can not see infrared light but special cameras can detect it. They can be used by police to see suspects at night or for firefighters to locate people in a smoke-filled building. It can also be used to see heat escaping houses. This will tell the person where to fit insulation.

They are often used for fibre optic communications. A single fibre can carry 1.5 million telephone conversations compared with 1000 conversations with copper wire! 

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Uses of Infra-red

The uses of infra-red waves are:

  • Thermal imaging/night vision cameras
  • Television remote controls 
  • short-range communications 
  • optical fibres
  • security systems 
  • cooking and heating
  • Any form of heat
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Visible light

This is the only part of the electromagnetic spectrum that humans can see. Different wavelengths correspond to different colours. If all of the wavelengths are being emitted were being emitted you would be able to see them all.

If the temperature of an object reaches 500 degrees Celsius Visible light and infra-red waves are emitted. You would say that the object is 'red hot'. If we keep on increasing the temperature it will come to a point that you can call it 'white hot'. It can also be used in fibre optics to send signals faster.

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Uses of Visible light

Here are some uses of invisible light.

  • vision 
  • Photography
  • illumination
  • Photosynthesis 
  • Fibre optic communications
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Ultraviolet waves(releases harmful radiation)

Ultraviolet waves are between violet light(ROYGBIV in visible light) and X-rays. They emit radiation which can harm your body with high doses.

Ultraviolet waves are harmful to the human eye and can cause blindness. Ultraviolet light is harmful to the skin. For example, too much UV from the sun or from a sunbed can give you sunburn and skin cancer. It can also age the skin prematurely(definition: before the due time for something)

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Uses of ultraviolet waves

  • Suntan beds 
  • Security pens or markers
  • Fluorescent lamps
  • detecting forged bank notes
  • disinfecting water 
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X-rays(ionising radiation)

X-rays carry a lot of energy. They have enough energy to ***** electrons from atoms. X-rays can go through the skin but they can not go through metal. They are actually refected by metal making a picture for people to see.

The general rule for X-rays is that denser the material the absorbs more it absorbs X-rays. For example, when a person is getting an X-ray scan, a photographic plate is put on both sides. the bone absorbs the x-rays; These cause a shadow on the plates.

X-rays can be used to kill cancer cells. To avoid any form of damaging healthy tissue, a very weak beam is shone at the area; When it finds a tumour the doctors increase the dose.

They are produced when electrons or other particles travelling at high speeds      

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Uses of X-rays

  • Medical X-rays
  • Recognizing the interior structure of things
  • Airport security scanners
  • Eliminating cancer cells 
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Gamma rays

These have the smallest wavelengths and have the highest amount of energy and more penetrating than X-rays. As you should know from Physics 1 that they can only pass through a few meters of lead or concrete. Gamma rays can kill living cells and can affect all organisms.

Gamma rays are two-faced(don't write two-faced in the actual exam but that is how I like to think of it.You could write in the exam about what you are going to read). Gamma rays are used to kill cancer cells but they are dangerous as they kill healthy human cells. They are also used to sterilise food and medical equipment. This makes the sterilised object safe to use.

Surgical equipment is irradiated with gamma rays to kill all bacteria that may be present.

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Uses of Gamma rays

  • Sterilising food and medical equipment
  • Disclosure of cancer and its treatment 
  • Radioactive Tracers to detect where substances go; human bodies, leaky pipes, machinery   
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A way to remember the Electromagnetic spectrum (mn

Radiowaves, Microwaves, Infrared, Visible light,  Ultraviolet waves, X-rays, Gamma rays

Ridiculous Monkeys Ignite Very Ultra eXterme Games   

Righteous Men Insist on Volunteering in Unique and eXpensive Goals

Rock Music Is Very Useful for eXperiments with Goats  

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