Monochromatic Light

Light is the fundamental source of energy on Earth. Light is of various wavelengths and is classified based on its properties and behaviour. Light exhibits various properties like Diffraction, Reflection, Refraction, Polarization and Interference. Electromagnetic radiations consist of various wavelengths of light.

Monochromatic lights are single-wavelength light, where mono refers to single and chroma means colour. Visible light of a narrow band of wavelengths is classified as monochromatic lights. It features a wavelength within a very short wavelength range. These lights are distinguished by their intensity or brightness, colour, the direction of propagation, and state of polarization.

Source and Applications of Monochromatic Light

The familiar source of monochromatic light is the LASER. LASER is abbreviated as Light Amplification By Stimulated Emission Of Radiation. A laser light results from one atomic transition with a specific single wavelength, which results in a monochromatic light beam.


Ultraviolet monochromatic devices are used in crime detection to scan specific and delicate evidence. Monochromatic light helps to recognize hidden bloodstains, fingerprints, fibres and also lesions that are located under the skin.


When we talk about light and spectrum, we are certain that one would have heard of a device known as spectrophotometers. Spectrophotometers are used to determine the amount of chemical substance in a particular substance by measuring the intensity of light. This device measures the intensity of light by measuring the amount of photons absorbed by the solution.

To transmit the particular narrow band of frequency, a device known as a monochromator is used. Monochromators are used to provide spectral isolation of the wavelengths from a beam of the light source. A monochromator uses the phenomenon of dispersion or diffraction. Polychromatic light is separated using a monochromator into a range of individual wavelengths. Narrowband among these individual wavelengths are selected to be separated.

The separation of lights into individual wavelength components is known as dispersion. In this device, a slit is used to block the unwanted wavelengths and pick a narrow band of wavelengths.

Two types of monochromators are:

  • Prism monochromators
  • Grating monochromators

In the prism monochromators, a prism is used as a dispersive element and in grating monochromators, a reflecting diffraction grating is used as a dispersive element.

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Frequently Asked Questions on Monochromatic Light

1. What type of light is LASER?

LASER is a monochromatic light.

2. Monochromator is used to separate which type of light?

It is used to separate polychromatic lights.

3. What are spectrophotometers used for?

Spectrophotometers are used to determine the amount of chemical substance.

4. What are the types of monochromators?

Two types of monochromators are:

  • Prism monochromators
  • Grating monochromators

5. What is the dispersive element used in grating monochromators?

A reflecting diffraction grating is used as a dispersive element in grating monochromators.

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