What is the difference between corpuscles and photons

Light is both a particle and a wave — and so, for that matter, is everything else. A single moving particle such as an electron can diffract and interfere with itself as if it were a wave, and believe it or not, an object as large as a car has a secondary wave character as it trundles along the road.

That revelation came in a barnstorming doctoral thesis submitted by the pioneering quantum physicist Louis de Broglie in He showed that by describing moving particles as waves, you could explain why they had discrete, quantised energy levels rather than the continuum predicted by classical physics.

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If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. The exact nature of visible light is a mystery that has puzzled man for centuries.

Greek scientists from the ancient Pythagorean discipline postulated that every visible object emits a steady stream of particles, while Aristotle concluded that light travels in a manner similar to waves in the ocean. Even though these ideas have undergone numerous modifications and a significant degree of evolution over the past 20 centuries, the essence of the dispute established by the Greek philosophers remains to this day.

One point of view envisions light as wave-like in nature, producing energy that traverses through space in a manner similar to the ripples spreading across the surface of a still pond after being disturbed by a dropped rock. The opposing view holds that light is composed of a steady stream of particles, much like tiny droplets of water sprayed from a garden hose nozzle. During the past few centuries, the consensus of opinion has wavered with one view prevailing for a period of time, only to be overturned by evidence for the other.

Only during the first decades of the 20th Century was enough compelling evidence collected to provide a comprehensive answer, and to everyone's surprise, both theories turned out to be correct, at least in part. In the early Eighteenth Century, the argument about the nature of light had turned the scientific community into divided camps that fought vigorously over the validity of their favorite theories. One group of scientists, who subscribed to the wave theory, centered their arguments on the discoveries of Dutchman Christiaan Huygens.

The opposing camp cited Sir Isaac Newton's prism experiments as proof that light traveled as a shower of particles, each proceeding in a straight line until it was refracted, absorbed, reflected, diffracted or disturbed in some other manner. Although Newton, himself, appeared to have some doubt about his corpuscular theory on the nature of light, his prestige in the scientific community held so much weight that his advocates ignored all other evidence during their ferocious battles.

Huygens' theory of light refraction, based on the concept of the wave-like nature of light, held that the velocity of light in any substance was inversely proportion to its refractive index. In other words, Huygens postulated that the more light was "bent" or refracted by a substance, the slower it would move while traversing across that substance.

His followers concluded that if light were composed of a stream of particles, then the opposite effect would occur because light entering a denser medium would be attracted by molecules in the medium and experience an increase, rather than a decrease, in speed. Although the perfect solution to this argument would be to measure the speed of light in different substances, air and glass for example, the devices of the period were not up to the task.

Light appeared to move at the same speed regardless of the material through which it passed. Over years passed before the speed of light could be measured with a high enough accuracy to prove that the Huygens theory was correct.

Despite the highly regarded reputation of Sir Isaac Newton, a number of prominent scientists in the early s did not agree with his corpuscular theory.

Some argued that if light consisted of particles, then when two beams are crossed, some of the particles would collide with each other to produce a deviation in the light beams. Obviously, this is not the case, so they concluded that light must not be composed of individual particles. When a beam of light travels between two media having differing refractive indices, the beam undergoes refraction, and changes direction when it passes from the first medium into the second.

This interactive tutorial explores how particles and waves behave when refracted through a transparent surface. The search for ether consumed a significant amount of resources during the Nineteenth Century before finally being laid to rest. The ether theory lasted at least until the late s, as evidenced by Charles Wheatstone's proposed model demonstrating that ether carried light waves by vibrating at an angle perpendicular to the direction of light propagation, and James Clerk Maxwell's detailed models describing the construction of the invisible substance.

Huygens believed that ether vibrated in the same direction as light, and formed a wave itself as it carried the light waves. In a later volume, Huygens' Principle , he ingeniously described how each point on a wave could produce its own wavelets , which then add together to form a wavefront. Huygens employed this idea to produce a detailed theory for the refraction phenomenon, and also to explain why light rays do not crash into each other when they cross paths.

When a beam of light travels between two media having different refractive indices, the beam undergoes refraction , and changes direction when it passes from the first medium into the second. To determine whether the light beam is composed of waves or particles, a model for each can be devised to explain the phenomenon Figure 3.

According to Huygens' wave theory, a small portion of each angled wavefront should impact the second medium before the rest of the front reaches the interface. This portion will start to move through the second medium while the rest of the wave is still traveling in the first medium, but will move more slowly due to the higher refractive index of the second medium.

Because the wavefront is now traveling at two different speeds, it will bend into the second medium, thus changing the angle of propagation. In contrast, particle theory has a rather difficult time explaining why particles of light should change direction when they pass from one medium into another. Proponents of the theory suggest that a special force, directed perpendicular to the interface, acts to change the speed of the particles as they enter the second medium.

The exact nature of this force was left to speculation, and no evidence has ever been collected to prove the theory. Another excellent comparison of the two theories involves the differences that occur when light is reflected from a smooth, specular surface, such as a mirror.

Wave theory speculates that a light source emits light waves that spread in all directions. Upon impacting a mirror, the waves are reflected according to the arrival angles, but with each wave turned back to front to produce a reversed image Figure 4. The shape of arriving waves is strongly dependent upon how far the light source is from the mirror. Light originating from a close source still maintains a spherical, highly curved wavefront, while light emitted from a distance source will spread more and impact the mirror with wavefronts that are almost planar.

The case for a particle nature for light is far stronger with regards to the reflection phenomenon than it is for refraction. Light emitted by a source, whether near or far, arrives at the mirror surface as a stream of particles, which bounce away or are reflected from the smooth surface. Because the particles are very tiny, a huge number are involved in a propagating light beam, where they travel side by side very close together.

Upon impacting the mirror, the particles bounce from different points, so their order in the light beam is reversed upon reflection to produce a reversed image, as demonstrated in Figure 4. Both the particle and wave theories adequately explain reflection from a smooth surface. However, the particle theory also suggests that if the surface is very rough, the particles bounce away at a variety of angles, scattering the light.