Newton's corpuscular theory of light (1704) proposes that light is composed of material particles which Isaac Newton called corpuscles. These particles are thrown in a straight line and at high speed by different sources of light (the Sun, a candle, etc.).
In physics, light is defined as a part of the radiation field called the electromagnetic spectrum. Instead, the term visible light is reserved to designate the part of the electromagnetic spectrum that can be perceived by the human eye. Optics, one of the oldest branches of physics, is responsible for the study of light.
Light has aroused human interest since time immemorial. Throughout the history of science there have been many theories about the nature of light. However, it was in the late 17th and early 18th centuries, with Isaac Newton and Christiaan Huygens, that their true nature began to be understood..
Thus began to lay the foundations for current theories about light. The English scientist Isaac Newton was interested throughout his studies to understand and explain the phenomena associated with light and colors; As a result of his studies, he formulated the corpuscular theory of light.
This theory was published in Newton's work called Opticks: or, a treatise of the reflexions, refractions, inflexions and colors of light (in Spanish, Optical or treatment of reflections, refractions, inflections and colors of light).
This theory was able to explain both the rectilinear propagation of light and the reflection of light, although it did not satisfactorily explain refraction..
In 1666, prior to enunciating his theory, Newton had carried out his famous experiment of decomposition of light into colors, which was achieved by making a beam of light pass through a prism.
The conclusion he reached was that white light is composed of all the colors of the rainbow, which in his model he explained by saying that the corpuscles of light were different depending on their color..
Reflection is the optical phenomenon whereby when a wave (for example, light) falls obliquely on the separation surface between two media, it undergoes a change of direction and is returned to the first along with a part of the energy of the movement.
The laws of reflection are as follows:
The reflected ray, the incident and the normal (or perpendicular), are in the same plane.
The value of the angle of incidence is the same as that of the angle of reflection. In order for his theory to comply with the laws of reflection, Newton assumed not only that the corpuscles were very small compared to ordinary matter, but that they also propagated through the medium without suffering any type of friction..
In this way, the corpuscles would collide elastically with the surface
separation of the two media, and since the difference in masses was very large, the
corpuscles would bounce.
Thus, the horizontal component of the momentum px would remain constant, while the normal component p would reverse its direction..
Thus, the laws of reflection were fulfilled, the angle of incidence and the angle of reflection being equal..
On the contrary, refraction is the phenomenon that occurs when a wave (for example, light) falls obliquely on the separation space between two media, with different refractive index.
When this happens, the wave penetrates and is transmitted for a half second along with a part of the energy of the movement. Refraction takes place due to the different speed at which the wave propagates in the two media.
An example of the phenomenon of refraction can be observed when an object (for example, a pencil or a pen) is partially inserted into a glass of water..
To explain refraction, Isaac Newton proposed that luminous particles increase their speed when passing from a less dense medium (such as, for example, air) to a more dense one (such as, for example, glass or water).
In this way, within the framework of his corpuscular theory, he justified refraction by assuming a more intense attraction of the luminous particles by the medium with higher density..
However, it must be considered that, according to his theory, at the instant in which a luminous particle from air strikes water or glass, it should undergo a force opposite to the component of its velocity perpendicular to the surface, which would entail a deviation of the light contrary to that actually observed.
The corpuscular theory of light has several errors:
Although Newton's theory signified an important step in understanding the true nature of light, the truth is that over time it proved quite incomplete..
In any case, the latter does not detract from it as one of the fundamental pillars on which future knowledge about light was built..
Yet No Comments