Various frequencies of radio waves are used for television and FM and AM radio broadcasts, military communications, mobile phones, ham radio, wireless computer networks, and numerous other communications applications.

Infrared light and radio waves We can feel the heat of infrared light because its energy is absorbed mostly by the skin. On the other hand, we cannot feel radio waves because these emit their energy deeper in the body, under the heat-sensitive cells of the skin.

Modern digital radio carries information as a digital signal, coded in the form of numbers. Millions of radio waves–carrying sound wave signals and digital signals–reach your receiver every second. The receiver’s tuner picks out a specific signal. Its amplifier strengthens that signal.

Radio waves can penetrate nonconducting materials, such as wood, bricks, and concrete, fairly well. They cannot pass through electrical conductors, such as water or metals.

When a direct electrical current is applied to a wire the current flow builds an electromagnetic field around the wire. This field sends a wave outward from the wire. When the current is removed, the field collapses which again sends a wave.

One way to make RF waves visible is with something like a radio telescope. An ordinary (light) telescope collects light and focuses it onto a receptor (CCD, photographic plate, the eye), thus making it possible to see the visible radiation emitted by a distant galaxy.

Radio waves have the longest wavelengths in the electromagnetic spectrum. These waves can be longer than a football field or as short as a football. Radio waves do more than just bring music to your radio. They also carry signals for your television and cellular phones.

Radio waves are used for communication such as television and radio. Radio waves are transmitted easily through air. They do not cause damage if absorbed by the human body, and they can be reflected to change their direction. These properties make them ideal for communications.

Radio waves are a type of electromagnetic (EM) radiation with wavelengths in the electromagnetic spectrum longer than infrared light. They have have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths from 1 millimeter to 100 kilometers.

Behaviour and uses of electromagnetic waves

1. Radio waves. Radio waves are used for communication such as television and radio.
2. Microwaves. Microwaves are used for cooking food and for satellite communications.
3. Infrared.
4. Visible light.
5. Ultraviolet radiation.

Examples of transverse waves include:

• ripples on the surface of water.
• vibrations in a guitar string.
• a Mexican wave in a sports stadium.
• electromagnetic waves – eg light waves, microwaves, radio waves.
• seismic S-waves.

One way to categorize waves is on the basis of the direction of movement of the individual particles of the medium relative to the direction that the waves travel. Categorizing waves on this basis leads to three notable categories: transverse waves, longitudinal waves, and surface waves.

Waves can be classified by how they move. As you have seen, one way to classify waves is according to the medium through which they travel. Another way to classify waves is by how they move. You have read that some waves transfer an up-and-down or a side-to-side motion.

Wave: The repeating and periodic disturbance that travels through a medium (e.g. water) from one location to another location. Wave Crest: The highest part of a wave. Wave Trough: The lowest part of a wave. Wave Height: The vertical distance between the wave trough and the wave crest.

Vocabulary

• crest. the top of a wave.
• wave. moving swell on the surface of water.
• wave height. the distance between a wave’s trough and crest.
• wavelength. the distance between the crests of two waves.
• wave trough. the lowest part of a wave.

A general form of a sinusoidal wave is y(x,t)=Asin(kx−ωt+ϕ) y ( x , t ) = A sin ( kx − ω t + ϕ ) , where A is the amplitude of the wave, ω is the wave’s angular frequency, k is the wavenumber, and ϕ is the phase of the sine wave given in radians.

The basic properties (parts) of a wave include: frequency, amplitude, wavelength and speed. Frequency is a measure of how many waves pass a point in a certain amount of time. The higher the frequency, the closer the waves are together and the greater the energy carried by the waves will be.

All waves have amplitude,wavelength and frequency. As the frequency increases, wavelength decreases.