Optical Instruments

What are Optical Instruments?

Optical instruments are devices which use light rays for one of two purposes.

  1. Enhancement of Images for Viewing
  2. Analysis of Light to determine different characteristic properties

We can define an optical instrument as:

A device that either processes light waves to enhance an image for viewing, or analyzes light waves to determine one of a number of characteristic properties.

Enhancement of Images

The most common types of optical instruments in this category are microscopes and astronomical telescopes. Astronomical telescopes are used to magnify distant objects in order to see them clearly.

There are of three types of Astronomical telescopes:

  1. Refracting telescopes: These use a combination of lenses to form a magnified image
  2. Reflecting telescopes: These instruments use a combination of mirrors to form a magnified image
  3. Catadioptric telescopes: These instruments use a combination of both lenses and mirrors to form images

Other than these three main types of optical telescopes, there are many others classified according to their varying tasks.


Microscopes are instruments designed to magnify small objects. A simple microscope uses only one lens for the sake of magnification whereas a compound microscope uses more than one lens. A compound microscope uses two lenses, one as the objective and the other as the eyepiece.


Camera another type of optical instrument. The objective is a converging lens. Light from a distant object is refracted through the objective lens and when the film is “exposed” the light for the short span, the image is etched onto it. A digital camera does not use films, however. The image, in this case, is captured by image sensors and reproduced in the many numbers of ways available.

Slide and film projectors

These are other examples of optical instruments. The image is illuminated and by using a combination of lenses magnified and projected onto a screen where it is displayed. Simple tools like magnifying lenses are also optical instruments.

Analysis of Light

Instruments like photometers (used to measure light intensity), polarimeter (used to measure the rotation of polarized light), and others are used to measure different characteristics of light waves.

For example, a refractometer is used to measure the refractive index of various materials when light passes through it.

Learn about different types of optical instruments and their working principles with the help of our expert tutors here at BYJU’S.

Test your knowledge on Different Optical Instruments

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