Waves in Communication

Waves in Communication

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When we want to say hello, we often wave our hands. But did you know there are many other ways to communicate? Sound waves are one way we use to talk to each other. When we speak, air moves through our vocal cords and creates vibrations that travel through the air until they reach our ears. However, sound waves can only travel so far before they get weaker.

For a long time, long-distance communication was slow and inefficient because messages had to be delivered by hand. But thanks to advancements in technology, we've found new ways to communicate using electromagnetic waves. These waves are part of the electromagnetic spectrum and have allowed us to communicate over long distances. Some of these methods are even useful for short distances. By using these waves, we've been able to make communication faster and more reliable.

Electromagnetic Waves in Communications

Take a look at the diagram below, which shows the electromagnetic spectrum. It's a way of showing how all types of electromagnetic radiation are spread out based on their frequency and wavelength. The waves with higher frequencies, such as gamma rays and x-rays, have shorter wavelengths and more energy. On the other hand, microwaves and radio waves have the lowest frequencies and energies, but their wavelengths are the longest.

Understanding the electromagnetic spectrum is important because it helps us understand how different types of waves are used in our daily lives. For example, radio waves are used for communication, while x-rays are used in medical imaging. It's amazing to think that all of these waves are present around us, even if we can't see or feel them!

The different sections of the electromagnetic spectrum are ordered by frequency and wavelength
The different sections of the electromagnetic spectrum are ordered by frequency and wavelength

Electromagnetic waves are super useful for sending and receiving messages. Different parts of the electromagnetic spectrum have different energies, frequencies, and wavelengths, which can make some parts better for certain uses than others. When it comes to communications, we typically only use the low-frequency parts of the spectrum. That's because radiation with high frequencies, like ultraviolet light, isn't very useful for long distances.

But scientists are looking into how ultraviolet light could be used for communication. Although UV light is absorbed by our atmosphere, it can still travel up to several miles when it comes from a strong enough source. Using ultraviolet light to communicate would have two main advantages. First, because it has a high frequency, it can send more information per second than lower frequency waves like visible light or infrared. Second, particles in the air can both absorb and scatter UV light, allowing a signal to spread out over a large area. Plus, because UV light can bounce around obstacles, it could be used to send messages between two places that can't see each other.

Radio Waves in Communications

In the electromagnetic spectrum, radio waves are the ones with the longest wavelengths and the lowest frequencies. Most radio wave frequencies pass right through the air, which makes them great for communicating over long distances. They also go right through the body, so they don't do any harm. The radio spectrum is a very large area. It has a range of wavelengths from 1 mm to 10,000 km, which is bigger than the Earth's diameter. So, radio waves with different lengths and speeds will act very differently. Most of the time, these waves are used to send messages, like in TV and radio broadcasts.

Electrical circuits that oscillate let us send and receive radio waves. When a radio wave gets into a conductor, it makes an alternating current. The speed of the radio wave is the same as the speed of the alternating current. This is how we use computers to encode information before sending it over radio waves and how we use computers to decode it after the wave has arrived.

Radio waves with a length of less than about 3 MHz are called short-wavelength waves. Radio waves like these are used to send information between two antennas that can be seen from each other. This means that the wave can only travel as far as the eye can see, which is about 64 km on the surface of the Earth. However, the waves are big enough to go through most buildings and plants without being stopped. We usually use high frequencies when we need to send a lot of information at once, like when we use radio, TV, cell phones, or radar. When radio waves have a frequency below 3 MHz, they start to bend over the horizon. This makes it possible for radios to send signals over hundreds of miles, following the shape of the Earth. The signal will go farther if the frequency is low. Unfortunately, less information can be sent per second when the frequency is low. Radio waves with wavelengths between 3 MHz and 30 MHz can also be scattered by charged particles in the ionosphere and sent back to the Earth's surface. This is called "skywave propagation," and it makes it possible for radio waves to travel between continents. Today, this method of communication is rarely used because the weather is too unpredictable.

Skywave propagation using radio waves, Pixabay

Visible Light Waves in Communications

Of course, we already use visible light to communicate naturally with each other, so we will discuss visible light purely as communications technology. In 1792 a Frenchman named Claude Chappe invented the semaphore telegraph system. The semaphore was a primitive way of transmitting information long-distance using visual signals. Tall towers were built within line of sight of each other, at distances between5and20miles depending on terrain. There would be a human operator at each tower with a spyglass, watching their neighbouring towers for signals. After receiving a message the operator would then relay the message to the next tower along. This was the precursor to the electrical telegraph, which would replace the semaphore less than a century later.

In the modern era, we use fibre optic cables to transmit signals as visible light. Fibre optic cables can be used to deliver high-speed internet. Fibre optic cables are made of flexible glass fibre, which allows electromagnetic waves to be internally reflected and therefore travel through the cable at the speed of light. These cables are safely enclosed by a plastic sheathing to protect the delicate glass fibres inside. Optical fibre cables can be used to transmit signals very long distances, as there is only a small loss of the signal due to scattering or absorption of the wave when it is reflected at the boundaries of the cable. The better quality glass allows for smaller losses as the wave travels through the cable.

A visible light ray travelling through a fibre optic cable via internal reflection, adapted from image by Chris Woodford  CC BY 3.0

Infrared Waves in Communications

Infrared light encompasses all electromagnetic radiation between700 nm(0.0007 mm) and1 mm. Infrared transmissions are mostly used in short-range communications. Your TV remote control is a common example of this. The main problem with infrared communications is that the waves will not pass through solid objects and are partially absorbed by the atmosphere, giving it a short-range. In some contexts (like the comfort of your own home) this can be turned into an advantage! An infrared TV remote in the living room will not interfere with similar devices in other rooms in the house because the signals cannot travel through walls. Furthermore, infrared transmitters are relatively cheap to make and have low power requirements, which keeps costs low for consumers

Infrared wavelengths are also used in fibre optic cables when the user wants to minimise the loss in the signal. Visible light in fibre optic cables can be more easily scattered or absorbed by impurities within the cable than infrared light, leading to more loss as the signal travels through the cable. However, due to the lower frequencies of infrared light, there is a smaller data transfer rate compared to the visible spectrum.

Satellite communications

One way of communicating on a global scale is to utilise satellites, often employed by satellite television companies and mobile phone networks. For instance, a mobile phone tower will transmit and receive data from many nearby mobile phones on the ground via radio waves. The mobile phone tower will then communicate with a satellite in geostationary orbit using microwaves. A geostationary satellite will remain stationary above a specific point of the Earth's surface at all times, so that communication with ground-based equipment can occur uninterrupted, 24/7. The microwave spectrum is used as it's not blocked by the Earth's atmosphere and can transmit more data per second than radio waves, because of their higher frequencies.

The satellite can then communicate with other mobile phone towers within a large area on the Earth's surface. Commercial satellites very rarely directly communicate with each other, signals must be relayed to receivers on the ground.

Using a satellite to communicate over long distances

A geostationary orbit can be achieved above the Earth by sending a satellite into orbit above the equator at around36000 kmabove the Earth's surface. At this height, a satellite will take exactly one day (23 hours and 56 minutes) to complete one orbit. If the satellite's orbit is in the same direction as the Earth's rotation then it will remain stationary in the sky as seen from Earth.

Waves in Communication - Key takeawaysMany different wavelengths of light in the electromagnetic spectrum are used in communications.The higher the frequency of a wave, the more data/information you can transmit per second.Electromagnetic radiation with frequencies higher than visible light becomes increasingly impractical.Radio waves have very high wavelengths and are typically used in television and radio broadcasts.Radio waves can be transmitted hundreds of miles at the lowest frequencies.Conductors can absorb and transmit radio waves, allowing information to be encoded and decoded electronically.Fibre optic cables transmit data using either visible or infrared light. They are useful because they can transmit a lot of data per second and have only a small loss of signal.Infrared spectrum is mostly useful in short-range communications, such as remote controls. Infrared radiation is partially absorbed by the atmosphere and completely blocked by obstacles.Satellites allow communications on a global scale. They use microwave radiation, due to the relatively high rate of data transfer compared to radio waves. Also, microwaves are transparent to the Earth's atmosphere.Most communications satellites are geostationary so that transmissions between satellites and ground-based equipment is uninterrupted.

Waves in Communication

What waves are used for communication? 

Radio waves, microwaves, infrared waves, visible light waves and (experimentally) ultraviolet waves. Waves with relatively low frequencies and high wavelengths.

What are the 7 types of waves? 

Radio waves, microwaves, infrared waves, visible light waves, ultraviolet waves, x rays, gamma rays

What are waves in communication?

A way to transmit and receive data

What causes waves in communication? 

Electromagnetic waves are essentially created by accelerating charged particles.

What is the importance of waves? 

Waves allow for communications and act as pathways between different energy stores.

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