Jethalal S. Zaveri
Prof. Muni Mahendra Kumar
The Quantum physics forced itself upon the scientific world at the beginning of this century with a discovery made in 1900 by Max Planck. He was trying to solve a specific problem, dealing with energy radiation. He wanted to know why objects glow bright and change colour when the temperature is increased (or decreased). Classical physics failed to give explanation to this simple phenomenon. Planck discovered that energy is not radiated (or absorbed) smoothly and continuously, but in spurts of specific amount or quanta (Planck himself was very unhappy with the implications of his discovery, as he had no intention to destroy the foundation of the Newtonian Physics.) (discrete packets). It was difficult to accept the concepts of the new theory, even after its precise and consistent mathematical formulation, because their implications were practically unbelievable.
In 1905, at the age of 26, Albert Einstein exploded upon the field of science with a force seldom exerted by a single scientist. He constructed the 'Theory of Relativity' in its complete form, entirely by himself. In the same year, he also declared a new way of studying the electromagnetic radiations, which was to become the basis of Quantum Physics. It took several years' work by a whole team of International group of physicists (The team consisted of (i) Neils Bohr, Denmark, (ii) Louis de Broglile, France (iii) Erwin Schrodinger (iv) Wolfgang Pauli, Austria, (v) Werner Heisenberg, Germany and (vi) Paul Dirac, England.) to complete the mathematical formulation of the Quantum Theory.
The dual nature is also exhibited by light, which can take the form of a particle (photon) or an electromagnetic wave. Radiation must be in the form of waves, because it produces well-known phenomena-interference associated only with waves. On the other hand, however, light also produces photo-electric effect It was Einstein's theory of light that a beam of light is composed of tiny particles, like a stream of bullets, each bullet being a photon. The problem is that we are talking about particles (photons) in terms of waves (wave-length and frequencies) and waves in terms of particles, thus producing the wave-particle duality paradox. Thus, while Planck described the processes of energy in terms of 'quanta', Einstein theorized that energy itself is quantized. Photons are particles of special kind. They are mass less and also travel with the speed of light.
In the early stages of atomic theory, physicists were puzzled by the dual nature of matter: how can anything be simultaneously particle (i.e. confined to a very small space) and a wave (which is spread out over a large area of space)? This apparent contradiction gave rise to a paradox. Physicists were confronted with two sets of repeatable experiences, each of which seemed to disprove the other. This resulted in the famous 'wave-particle duality’, which is fundamental to Quantum theory.
The paradox became more paradoxical when Louis de Broglie (in 1924) dropped a bomb, which demolished what was left of classical view. He proposed, "Not only are waves particles, but particles are also waves". It was bewildering enough when electromagnetic waves (light) behaved like particles, but when electrons, which are particles, were found to behave like waves2 (The famous Davisson-Germer-Experiment showed electrons reflecting off a crystal surface in a way that could be explained only if they were waves.), the effect was stunning. Subsequent experiments revealed that not only subatomic particles but atoms and molecules also have associated matter-waves. Theoretically, everything - tables, cars, men - has a wavelength but their wavelengths are so small that they are not noticeable.
