Corpuscular theory of light

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The corpuscular theory of light states that light is composed of small discrete particles called corpuscles. This theory was put forward by the great scientist Sir Isaac Newton, who succeeded in explaining some important properties of light with this theory. The theory, however, failed for other important phenomena. The photoelectric effect, which was explained in the early 20th century, is considered to be an incarnation of the corpuscular theory of light.

Acceptance of the corpuscular theory of light

The corpuscular theory was widely accepted in the 18th and 19th centuries, as a means to explain some of the most important phenomena concerned with light. The property of the rectilinear propagation of light was explained by this theory, which considered light to be made up of particles without any mass.

The phenomenon of reflection was also explained by Newton's claim that the boundaries of the various propagation media exert repulsive forces on the particles of light. Refraction was explained in a similar manner, with the media believed to be exerting attractive forces. This is how Newton tried to apply the laws of motion to the propagation of light energy.

Failure of the corpuscular theory

The corpuscular theory of light was replaced by Maxwell's electromagnetic wave theory of light, which states that light is propagated due to the action of electric and magnetic fields in such a way as to permit the wave energy to travel through space.

The corpuscular theory was proven to be unacceptable because of the following main reasons:

  1. The phenomena of reflection and refraction may occur at the boundary of a translucent medium. According to the corpuscular theory, this would mean the presence of both repulsive and attractive forces at the surface of the medium, which is impossible. The wave theory of Huygen, which was put forward around the same time as Newton's theory was able to explain refraction and refelction in a better manner.
  2. The phenomena of interference, polarization and diffraction cannot be explained by the corpuscular theory.

Modern theories of the propagation of light based on Maxwell's theory of electromagnetic waves, have been supplanted by the principles of quantum mechanics and wave particle duality and have succeeded in overcoming the main drawbacks of the older theories.