Throughout history, mankind has thought about the nature of such a phenomenon as light. From ancient times to the present day, ideas about it have changed and improved. The most popular hypotheses tended to be that light is a particle or a wave. The branch of modern science that studies the nature and behavior of light is called optics.
History of the development of ideas about light
According to the ideas of ancient Greek philosophers, such as Aristotle, light is the rays emanating from the human eye. Through the ether, a transparent substance that fills space, these rays spread, allowing a person to see objects.
Another philosopher, Plato, suggested that the sun is the source of light on Earth.
The philosopher and mathematician Pythagoras believed that tiny particles fly out of objects. Getting into the human eye, they give us an idea of the appearance of these objects.
Despite the seeming naivety, these hypotheses laid the foundation for further development of thought.
So, in the 17th century, the German scientist Johannes Keplerexpressed a theory close to the ideas of Plato and Pythagoras. In his opinion, light is a particle, or more precisely, a stream of particles propagating from some source.
Newton's Corpuscular Hypothesis
Scientist Isaac Newton put forward a theory that combined to some extent conflicting ideas about this phenomenon.
According to Newton's hypothesis, light is a particle whose movement speed is very high. Corpuscles propagate in a homogeneous medium, moving uniformly and rectilinearly from the light source. If the flow of these particles enters the eye, then the person observes its source.
According to the scientist, the corpuscles were of different sizes, giving the impression of different colors. For example, large particles contribute to the fact that a person sees red. He argued the phenomenon of reflection of a stream of light by the rebound of particles from a solid barrier.
The scientist explained the white color by a combination of all the colors of the spectrum. This conclusion is the basis of his theory of dispersion, a phenomenon he discovered in 1666.
Newton's hypotheses found great acceptance among his contemporaries, explaining many optical phenomena.
Huygens' wave theory
Another scientist of the same time, Christian Huygens, did not agree that light is a particle. He put forward the wave hypothesis of the nature of light.
Huygens believed that all the space between objects and in the objects themselves is filled with ether, and light radiation is pulses, waves propagating in this ether. Each section of the ether, which reaches the lightwave becomes a source of so-called secondary waves. Experiments on the interference and diffraction of light confirmed the possibility of a wave explanation of the nature of light.
Huygens' theory did not receive much recognition in his time, as most scientists tended to consider light to be a particle. However, it was subsequently adopted and refined by many scientists, such as Jung and Fresnel.
Further development of views
The question of what light is in physics continued to occupy the minds of scientists. In the 19th century, James Clerk Maxwell developed the theory that light radiation is high-frequency electromagnetic waves. His ideas were based on the fact that the speed of light in a vacuum is equal to the speed of electromagnetic waves.
In 1900, Max Planck introduced the term "quantum" into science, which translates as "portion", "small amount". According to Planck, the radiation of electromagnetic waves does not occur continuously, but in portions, in quanta.
These ideas were developed by Albert Einstein. He suggested that light is not only emitted, but also absorbed and propagated by particles. To designate them, he used the word "photons" (the term was first proposed by Gilbert Lewis).
Particle-wave duality
Modern explanation of the nature of light lies in the concept of wave-particle duality. The essence of this phenomenon is that matter can exhibit the properties of both waves and particles. Light is an example of such matter. The studies of scientists who have come to seemingly opposite opinions are confirmation of the dual nature of light. Light is both a particle and a wave at the same time. The degree of manifestation of each of these properties depends on the specific physical conditions. In certain cases, light exhibits the properties of an electromagnetic wave, confirming the wave theory of its origin, in other cases, light is a stream of corpuscles (photons). This gives grounds to state that light is a particle.
Light became the first matter in the history of physics, which recognized the presence of corpuscular-wave dualism. Later, this property was discovered in a number of other matters, for example, wave behavior is observed in molecules and nucleons.
Summarizing, we can say that light is a unique phenomenon, the history of the development of ideas about which has more than two thousand years. According to the modern understanding of this phenomenon, light has a dual nature, showing the properties of both waves and particles.
