ChemTalk

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What we call “light”, physicists call “electromagnetic radiation”. Most light that we’re familiar with is the visible sort; the light we see emitted from a lamp, or the Sun, or a bonfire. But, you may have heard of so-called “invisible light”, such as the UV rays responsible for sunburns or the gamma rays that come from radioactive materials. Electromagnetic radiation can be understood as a more generic term that includes both visible and invisible light. Other everyday examples of electromagnetic radiation include X-rays, microwaves, and radiowaves.

In more technical terms, electromagnetic radiation is an energy generated by oscillating waves through a magnetic or electric field. This radiation is characterized by the movement of electrically-charged particles. However, unlike most other physical waves that require an object to pass through, such as sound waves, electromagnetic radiation can travel through empty space. As waves, each type of electromagnetic radiation is defined by its wavelength, with visible light falling within a certain range of wavelengths (380nm-740nm).

## Frequency, Wavelength, and Amplitude

Electromagnetic radiation displays wavelength, amplitude, and frequency properties. Wavelengths represent the distance between the maximum and minimum points of a wavelength, representing an oscillation cycle completion.

Amplitude represents the distance from the maximum/minimum point of a wave to the middle, or the wave’s height. Along with wavelengths, amplitude can indicate the brightness or intensity of a wave – the greater the amplitude, the more energy released by the wave.

Frequency is the total number of wave cycles that occur in a second. Measured in Hertz, frequency measures the number of oscillations a wavelength generates within a certain time frame. Directly proportional to energy release, frequency and energy are related in the equation E= hv, where h represents the Planck constant (6.62607 x 10-34).

Given the wavelength and frequency, the velocity of a wavelength can be determined with the equation: velocity=λν.

## Electromagnetic Spectrum

The electromagnetic spectrum categorises different electromagnetic wavelengths based on frequencies and wavelengths. As wavelengths increase, the frequencies decrease. Conversely, as wavelengths decrease, frequencies increase. The electromagnetic spectrum accounts for both properties and groups radiations accordingly.

This range includes associated wavelength and photon energies. Each segment of the spectrum display different properties and matter interactions. These wavelengths include gamma rays, microwaves, infrared waves, and X-rays.

Whenever a charged particle experiences significant change in its velocity, electromagnetic radiation is produced. The charged particle thus produces and releases energy through radiation. Moreover, this phenomenon is commonly seen in the oscillating waves in a radio antenna that generates electromagnetic waves.

In turn, another radio antenna tuned to the same frequency as the outgoing wave can then receive the radiating oscillations. Any system that produces radiation of a certain frequency can then receive radiations of that same frequency. The Sun, for example, a system that produces radiation covering a broad spectrum of frequencies, can be defined as an electromagnetic radiation generator.

Approximately a kilometer in wavelength, radio waves are transmitted by broadcasters, TV and cell phones. Due to their long wavelengths, radio waves have low frequencies and energy levels.

• Microwaves

Used to warm up food and other items, microwaves are also used for transmitting information through substances like clouds or rain. Microwave wavelengths are measured in centimeters.

• Visible Light

This segment of the electromagnetic spectrum includes a range of different colors that are visible to the human eye. Different wavelengths correspond to different colors, ranging from violet with a wavelength of 380 nm to red with a wavelength of 740 nm.

This radiation can be released as thermal or heat energy, and can also be bounced back. Infrared radiation has wavelengths just above the visible spectrum of 740 nm (red), hence the name “infrared”. In meteorology, infrared radiation can provide us information on weather conditions.