5 Things radio waves and microwaves have in common

Electromagnetic Nature

Radio waves and microwaves are both parts of the electromagnetic spectrum; they share a number of the same core characteristics, notably that they travel at the speed of light, approximately 300,000 kilometers per second. The frequency range for radio waves spans from 3 kHz to 300 GHz, while microwaves occupy the higher frequency band between 300 MHz and 300 GHz. Wi-Fi networks also operate at 2.4 GHz and 5 GHz frequencies, in the microwave region, and can attain data transfer rates of 1.2 Gbps under ideal conditions.

A typical FM radio wave with a frequency of about 100 MHz has much lower energy than a microwave with a frequency of 2.4 GHz. microwaves are efficiently absorbed by water molecules, which is what happens in your microwave oven. A typical household microwave oven runs with 1,000 watts of power at 2.45 GHz to heat up your lunch or leftovers in an efficient way. Radio waves are used in broadcasting; for example, an AM transmitter of 50,000 watts has a very wide signal range over hundreds of kilometers without causing significant heating of the outside environment.

Radio waves and microwaves support both long-distance and high-speed data transmission in communication technologies. Satellite communication systems use frequencies in the microwave range, typically between 1 GHz and 30 GHz. A geostationary satellite requires about 1 kW of transmitter power to set up a reliable communication link over a distance of 35,786 km. By contrast, terrestrial radio systems-for instance, those transmitting from mobile phone towers-run lower powers in the range of 20 to 40 watts per antenna over cells of 1-5 kilometers.

Bluetooth devices run at 2.4 GHz, sending data within a distance of 10 meters, operating very effectively with minimal power on such small battery-run devices as wireless earbuds. Larger systems, like radar, which use high-powered microwaves to detect objects, require output levels to as high as 1 megawatt. A weather radar that operates at 5 GHz can detect precipitation patterns as far away as 300 kilometers, supplying vital data for meteorological studies and aviation safety.

Speed

Electromagnetic waves, including radio waves and microwaves, travel at the speed of light in a vacuum, approximately 299,792 kilometers per second. A satellite in geostationary orbit at 35,786 kilometers from Earth can relay a signal to a ground station in just 0.12 seconds.

In air, the velocity of radio waves is practically the same as that in a vacuum; while passing through glass or water, it slows down considerably. For example, in water, the speed of electromagnetic waves decreases to approximately 225,000 kilometers per second, depending on the purity and temperature of the water.

Cellular phone systems use electromagnetic waves to send voice and data signals around almost instantaneously. A 4G LTE network at 2.6 GHz will ensure that packets of data jump from base stations to user devices in less than 50 milliseconds for most users. The older 3G networks operate on a lower frequency with slower rates, hence latencies higher than 100 ms, rendering them unsuitable for high-speed applications.

Because radar systems rely on microwaves to detect and track objects, calculating the distance to an object is determined by how long it takes to have a wave travel to the object and back. For example, a weather radar is working at 10 GHz and can detect storm systems as far away as 300 kilometers and give updates almost instantly every few seconds.

Wavelength and Frequency Relationship

The relationship between wavelength and frequency is a fundamental property of electromagnetic waves and is defined by the equation $c=\lambda \cdot f$, where $c$ is the speed of light (approximately 299,792 kilometers per second), $\lambda$ is the wavelength, and $f$ is the frequency. This inverse relationship means that as the frequency of a wave increases, its wavelength decreases. For example, a radio wave at 100 MHz (commonly used for FM broadcasting) has a wavelength of approximately 3 meters, while a microwave at 2.4 GHz (used in Wi-Fi) has a wavelength of just 12.5 centimeters.

Long-wavelength radio waves are better for long-distance communications, because they can diffract around obstacles like buildings and mountains. The AM band, from 530 kHz (kilo Hertz) to 1,710 kHz contains long-wavelength radio waves and the AM radio wave at 1 MHz has a wavelength of 300 meters. With only 50,000 watts of transmitter power it covers areas up to 250 kilometers in radius. Whereas in FM radio, smaller wavelengths are used-88-108 MHz-that give better audio quality but cover smaller areas, typically up to 100 kilometers, requiring the antenna to be higher to maximize the range.

Microwaves are a form of radar operating at 10 GHz and having a wavelength of 3 centimeters. It is this very short wavelength that can accurately detect small objects, like raindrops in weather radar or aircraft in aviation radar systems. A radar with 3-centimeter wavelength resolution would easily separate objects only a few meters apart, situated hundreds of kilometers away, enabling highly detailed tracking and imagery.

Because of their wavelength, 2.4 GHz and 5 GHz Wi-Fi networks offer different trade-offs between range and speed. The signal of a 2.4 GHz has a 12.5-centimeter wavelength that can penetrate through the walls and other obstacles much better, giving it broader coverage; however, the wavelength of a 5 GHz is 6 centimeters and allows even faster data rates but at a shorter effective range. The newest generation of dual-band routers uses both frequencies to balance these advantages, achieving speeds up to 1.2 Gbps while keeping indoor coverage over distances of 30-50 meters.

Non-ionizing

Radio waves and microwaves are forms of non-ionizing radiation, this characteristic sets them apart from ionizing radiation, such as X-rays or gamma rays, which carry energies above 10 electron volts (eV) and can break chemical bonds. For example, a 2.4 GHz microwave used in Wi-Fi has an energy of approximately 1×10−51 \times 10^{-5}1×10−5 eV, far below the threshold for ionization.

Most phones normally work within a frequency of between 700 MHz and 2.7 GHz with a power range of 0.1 to 2 W. Indeed, studies have shown that the specific absorption rate from such devices was well within the 1.6 W/kg set by regulatory agencies for safety consideration as acceptable limits of human exposure. It follows that X-rays used in medical imaging involve far higher energies, on the order of thousands to millions of electron volts, and therefore require stringent controls on human exposure because of their ionizing nature.

Another example of practical use of non-ionizing radiation is microwave ovens. Operating at 2.45 GHz, these ovens emit radiation with enough energy to excite water molecules, generating heat without changing their molecular structure. The power output of a conventional microwave oven is 1,000 watts and can warm up food to 100 degrees Celsius in a minute or two.

Magnetic Resonance Imaging (MRI) is a technique that uses radio waves at a frequency of 10 MHz to 300 MHz to produce detailed images of internal body structures. An MRI scanner usually operates at a power level of 15 kW. Exposures must be carefully controlled to avoid thermal effects on tissues. Similarly, industrial heating systems also use microwaves of frequency in the range of 915 MHz to 2.45 GHz for material drying or curing, accomplishing accurate temperature control without affecting the chemical properties of the products under process.

Used in Communication

Radio waves usually have frequencies from 3 kHz to 300 MHz. Radio waves are utilized in AM and FM radio broadcasting. An AM radio station broadcasts at 1,000 kHz (1 MHz); if a transmitter radiates 50,000 watts of power, it can send signals to distances of more than 100 kilometers. FM radio, on the other hand, has a much higher frequency of 88 MHz to 108 MHz, with better audio quality but a more limited range of about 50-100 kilometers, depending on the terrain and transmitter power, which ranges from 100 to 100,000 watts.

Microwaves have frequencies from 300 MHz to 300 GHz and are used in high-speed data communication systems. For example, Wi-Fi operates at 2.4 GHz and 5 GHz frequencies, supporting data rates of up to 1.2 Gbps over short distances of 30-50 meters indoors. Cellular networks also operate at similar microwave frequencies. Operating between 700 MHz and 2.7 GHz, 4G LTE has an average download of 20-30 Mbps. Meanwhile, newer 5G wireless uses as much as 28 GHz airwaves to achieve download speeds of more than 1 Gbps in metropolitan areas. Small cell towers for 5G typically transmit at power levels of 10 to 40 watts to make sure the demand is high with dense network coverage.

Satellite communication heavily utilizes microwaves due to their ability to penetrate the atmosphere. Satellites stationed in geostationary orbits 35,786 kilometers above the Earth’s surface send signals back to Earth in Ku-band frequencies (12-18 GHz) and C-band frequencies (4-8 GHz). Most satellites have a single transponder power output of 100 to 200 watts and are capable of transmitting several hundred channels of high-definition television or internet access.