Electromagnetic Spectrum | Definition, Types, Diagram

The electromagnetic spectrum is a long-range series of all electromagnetic waves that arranged according to frequency and wavelength. The sun, stars, clusters, earth, and other bodies radiate electromagnetic radiation having different wavelengths. Electromagnetic waves pass through space at the speed of the light in the form of sinusoidal waves.

electromagnetic spectrum

Types of the electromagnetic spectrum

The electromagnetic spectrum is categorized into three different categories. They categorized with respect to their properties or physical behavior that they show when they pass through different mediums.

Types of electromagnetic spectrum



  • Continuous spectrum:

A continuous spectrum might be white light, but it is only a part of the electromagnetic spectrum. There are many wavelengths than we can see with our human eyes. The continuous spectrum includes ultraviolet,  radio waves, X-rays, microwaves and infrared and gamma rays.

A continuous spectrum is produced by solids, liquids & dense gases produce – no “gaps” in wavelength of light produced:

Continuous spectrum

  • Emission spectrum:

The emission spectrum of a chemical compound or chemical element is the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule making a transition from a high energy state to a lower energy state. Each element emission spectrum is unique and have specific properties.

The emission spectrum is produced by rarefied gases – emission only in narrow wavelength regions:

Emission spectrum

  • Absorption spectrum:

The absorption of electromagnetic radiation is how matter takes up a photon’s energy. This means that the typical electrons bound in atoms. These atoms transform electromagnetic energy into the internal energy of the absorber (like thermal energy). This effect gradually reduces the intensity of the light waves as they propagate through a medium. Also, the absorption of the waves does not depend on their intensity (linear absorption), in certain conditions the medium’s transparency changes by a factor that varies as a function of wave intensity, and saturation absorption (or nonlinear absorption) occurs.

Absorption spectrum Gas atoms absorb the same wavelengths as they usually emit and results in an absorption line spectrum:

Absorption spectrum



  • Inline spectrum the Electron transition takes place between energy levels in this result the emission or absorption lines formed.
  • Different elements produce different spectra because different elements have different atomic structures.









Emission/Absorption of Radiation by Atoms


    1. Radiative (or Stimulated) absorption:

A photon with energy (Eg = hn = E2 – E1) excites an electron from lower energy levels. This means that the electron in the lower orbit gain energy and become excited and jump in the high energy orbit.

1. Radiative (or Stimulated) absorption

 This can only occur if    Eg = hn = E2 – E1

Types of Radiative recombination

  1. Spontaneous emission:

In spontaneous emission, the electron minimizes its total energy by emitting a photon and making the transition from E2 to E1.

Spontaneous emission

      Emitted photon has energy    Eg = hn = E2 – E1

  1. Stimulated emission:

stimulated emission photon is strongly coupled with the electron, causing an electron to decay to lower energy level, releasing a photon of the same energy.

Stimulated emission

                              Can only occur if     Eg = hn = E2 – E1  Also, hn = hn

  1. Radioactive recombination/emission:

Electron makes the transition to lower energy level (hn = E2 – E1) and emits a photon with energy. In this, the electron loses energy in the form of photon and jumps from high level orbital to the low level orbital.

  hn = E2 – E1


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