Electromagnetic Radiation and Atomic Spectra

Electromagnetic Radiation and Atomic Spectra

The electromagnetic spectrum consists of seven regions- radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays. Radio waves, microwaves, visible light, x-rays, etc. have different frequencies or wavelengths and are called electromagnetic radiation. Electromagnetic radiation interacts with atoms and molecules. A spectrum of radiation is emitted or absorbed as a result of this interaction. Each chemical element has a unique atomic spectrum like every human has a unique fingerprint. Scientists study the atomic spectra of different atoms and molecules to identify elements. Atomic spectra are also studied to analyze the chemical composition of stars and other bodies.

Electromagnetic Radiation

Oscillating electric and magnetic fields produce electromagnetic radiation. The flow of energy with simultaneously varying electric and magnetic fields is termed electromagnetic radiation. It is also known as EM radiation. Visible light is an example of EM radiation. Other waves like radio waves, microwaves, infrared, ultraviolet, gamma rays, etc. are also electromagnetic in nature and are called electromagnetic radiation.

Properties of Electromagnetic Radiation

• Electromagnetic radiation travels through both vacuum and medium
• Every electromagnetic radiation has a distinctive frequency and wavelength
• An Electromagnetic wave or an EM radiation has dual nature, i.e. it acts as a particle and a wave
• The wave nature of an EM wave is defined by wavelength, frequency, and velocity
• Electromagnetic radiation travels with the speed of light
• The electric and magnetic fields oscillate perpendicular to each other and are both perpendicular to the direction in which the EM wave propagates

Electromagnetic Spectrum

The electromagnetic spectrum is a range of electromagnetic waves of different frequencies. It is divided into seven regions with varying frequencies or wavelengths. The seven regions are-

1. Radio Wave: it has a frequency of around 106 Hertz.
2. Microwave: it has a frequency of around 1010 Hertz
3. Infrared: it has a frequency of around 1013 Hertz.
4. Visible Light: it has a frequency of around 1015 Hertz.
5. Ultraviolet: it has a frequency of around 1016 Hertz.
6. X-ray: it has a frequency of around 1018 Hertz.
7. Gamma: it has a frequency of around 1020 Hertz.

The electromagnetic spectrum expands into a wider range of frequencies, covering waves of frequencies above 25 Hz. Radio waves, microwaves, and infrared have lower frequencies but longer wavelengths. While x-rays and gamma rays have higher frequencies but shorter wavelengths. Shorter wavelengths correspond to higher energies, so an x-ray is high-energy radiation.

What is Atomic Spectra?

Atomic spectra are the interactions of electromagnetic radiation with matter. The study of this interaction is called spectroscopy. When electromagnetic radiation passes through matter, it interacts with the atoms and molecules of matter. Electromagnetic radiation can be passed through matter and the obtained electromagnetic spectrum can be analysed. The electromagnetic spectrum tells a lot about matter. Chemists study the electromagnetic spectrum of different chemical substances to identify the elements. An atom consists of electrons. Each electron revolves around the nucleus in stationary orbits of fixed energies. When an electron jumps from a lower energy level to a higher energy level in an atom, it absorbs energy in the form of electromagnetic radiation. While, when an electron makes a transition from a higher energy level to a lower energy level, it emits energy in the form of electromagnetic radiation. Collection of all the emitted and absorbed radiations of an atom at a particular temperature, pressure, etc., are the atomic spectra of that atom.

Properties of Atomic Spectra

The characteristics of atomic spectra are as follows:

• It is a pure line spectrum
• It is an absorption line spectrum
• It is an emission line spectrum
• It should be an absorption band spectrum

Types of Atomic Spectra

Broadly, there are two types of atomic spectra. These are-

1. Absorption Spectra.
2. Emission Spectra.

Absorption Spectra

An electromagnetic radiation is incident on a chemical substance. The obtained electromagnetic spectrum is then analysed. Some dark lines are observed on the atomic spectrum. These dark lines correspond to the absorption of some wavelengths of the incident EM radiation. The obtained electromagnetic spectrum is obtained as a consequence of absorption of radiations and is called the absorption spectrum.

Emission Spectra

The electromagnetic spectrum obtained as a result of the emission of radiation is called the emission spectrum. The emission spectra are further classified into two types depending upon the radiation source:

1. Continuous Spectra.
2. Line Spectra.

Continuous Spectra

White light passing through a prism is split up into seven different colour bands. Each colour band seems to be merged with the next one appearing continuous. Such spectra are known as continuous spectra.

Line Spectra

Electromagnetic radiation emitted from heating some substance, like a volatile salt, can be incident on a substance to give an electromagnetic spectrum. Coloured lines are obtained, separated by dark gaps. The coloured lines occur at the same places where dark lines were obtained in absorption spectra. Such spectra are known as emission line spectra or simply as line spectra. Knowing the electromagnetic radiation definition or the electromagnetic spectrum definition is not enough. The understanding of the nature of electromagnetic radiation and its interaction with matter is important to study the composition of substances. The mere jumping of the electrons across energy levels gives rise to such a wide branch called spectroscopy. Atomic spectroscopy is used in pharmaceutical companies to identify chemical elements. In chemistry, atomic spectra of elements are studied to understand the structure of atoms and molecules. Environmental scientists are using atomic spectroscopy to monitor the changes in the atmosphere around the globe. Atomic fluorescence spectroscopy is used by scientists too.