Quantum A “packet” of energy

But we must be careful with our words when we say these are different types of photon, we do not mean that they are different in kind, only in magnitude. In kind, all photons are identical each comprises a packet of energy, which is termed a quantum, because the amount of energy in each photon is quantized (or fixed ). 

Each of the normal modes in the harmonic approximation is a traveling wave in the crystal and represents a packet of energy by analogy with the wave/photon duality of electromagnetic radiation, the wave packets in crystals are called phonons. The energy of each phonon can be quantified either classically or quantum mechanically. Since the normal modes are independent, the vibrational partition function for the crystal is simply the product of the individual partition functions for each phonon. These are known analytically for harmonic oscillators. The corresponding classical and quantum mechanical partition functions for the crystal are ... 

Quantum theory considers radiation as a stream of energy packets - photons or quanta - travelling through space at a constant velocity (c when in a vacuum). The energy of a photon is related to the frequency of the radiation, as defined in wave theory, by the expression... 

The Bohr model of the atom took shape in 1913. Niels Bohr (1885-1962), a Danish physicist, started with the classic Rutherford model and applied a new theory of quantum mechanics to develop a new model that is still in use, but with many enhancements. His assumptions are based on several aspects of quantum theory. One assumption is that light is emitted in tiny bunches (packets) of energy call photons (quanta of light energy). 

Light is quantized, which means it consists of a stream of energy packets. Each packet is called a quantum, also known as a photon. 

Planck s result was a real surprise. Physicists had always assumed that the energy of matter was continuous, which meant that the transfer of any quantity of energy was possible. Now it seemed clear that energy is in fact quantized and can only be transferred in discrete units of size hv. Each of these small packets of energy is called a quantum. A system can transfer energy only in whole quanta. Thus energy seems to have particulate properties. 

It has proven useful to view electromagnetic radiation as the propagation of a collection of discrete packets of energy called photons or quanta, as proposed by Max Planck in 1900 in conjunction with his quantum theory, in this view, each photon of frequency v is considered to have an energy of... 

More than a century has passed since Planck discovered that it is possible to explain properties of the blackbody radiation by introducing discrete packets of energy, which we now call photons. The idea of discrete or quantized nature of energy had deep consequences and resulted in development of quantum mechanics. The quantum theory of optical fields is called quantum optics. The construction of lasers in the 1960s gave impulse to rapid development of nonlinear optics with a broad variety of nonlinear optical phenomena that have been... 

In order to understand fully the practical aspects of absorption theory, it is necessary to digress briefly into quantum theory. For this explanation, let us consider that radiation takes the form of a stream of particles of packets of energy, called photons (instead of the waves as previously mentioned). Each atom and molecule exists in a number of energy levels, or states, and a change of level will require the absorption (or emission) of an integral number of photons (or unit energy called a quantum, in quantum theory). 

To explain the photoelectric effect, Einstein assumed that the radiant energy striking the metal surface behaves like a stream of tiny energy packets. Each packet, which is like a particle of energy, is called a photon. Extending Planck s quantum theory. 

Bohr postulated that there can be only certain discrete orbits for the electron around a nucleus—called stationary states—and that to go from one state to another, an atom must absorb or emit a packet of just the right amount of energy—a quantum. He then proceeded to predict the position of the lines in the hydrogen spectrum based on Balmer s formula, Planck s energy packets, the mass and charge on an electron, and his quantized orbits. 

But it is the second theory of modern physics that has exerted by far the more important influence in attempts to understand the periodic system theoretically. Quantum theory was actually born in the year 1900, some 14 years before the discovery of atomic number. It was first applied to atoms by Niels Bohr, who pursued the notion that the similarities between the elements in any group of the periodic table could be explained by their having equal numbers of outer-shell electrons. " The very notion of a particular number of electrons in an electron shell is an essentially quantumUke concept. Electrons are assumed to possess only certain quanta, or packets, of energy, and depending on how many such quanta they possess, they lie in one or another shell around the nucleus of the atom. 

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