Photoelectric effect quantum mechanics

Albert Einstein s 1905 work on the photoelectric effect paved the way for one of the greatest advances of twentieth-century science, the theory of quantum mechanics. Light had always been regarded as a wave. Quantum mechanics introduced the concept of light being transmitted in wave packets, or photons, that have particle-like qualities as well as wave-like qualities. 

Schrodinger s equation is widely known as a wave equation and the quantum formalism developed on the basis thereof is called wave mechanics. This terminology reflects historical developments in the theory of matter following various conjectures and experimental demonstration that matter and radiation alike, both exhibit wave-like and particle-like behaviour under appropriate conditions. The synthesis of quantum theory and a wave model was first achieved by De Broglie. By analogy with the dual character of light as revealed by the photoelectric effect and the incoherent Compton scattering... 

It does not provide much historical perspective on the development of quantum mechanics. Subjects such as the photoelectric effect, black-body radiation, the dual nature of electrons and photons, and the Davisson and Germer experiments are not even discussed. 

Textbooks frequently cite this work as strong empirical evidence for the existence of photons as quanta of electromagnetic energy localized in space and time. However, it has been shown that [8] a complete account of the photoelectric effect can be obtained by treating the electromagnetic field as a classical Maxwellian field and the detector is treated according to the laws of quantum mechanics. 

What is not so well known about Einstein is that he made contributions to the development of modern chemistry, particularly to the area of quantum mechanics. The Nobel Prize Committee awarded Einstein the Nobel Prize in physics in 1921 for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect. His explanation of the photoelectric effect helped to validate Planck s view of quantized energy, and has become the basis of the quantitative laws of photochemistry. 

It is one of the ironies of twentieth century science that, although his work on the photoelectric effect helped to advance quantum mechanics, Einstein came to be its chief critic. It was his antagonism toward the probabilistic and nondeterministic nature of quantum phenomena that prompted Einstein to make the often-quoted remark, I cannot believe that God would choose to play dice with the universe. ... 

The mathematical treatment of the Rutherford-Bohr atom was especially productive in Denmark and Germany. It led directly to quantum mechanics, which treated electrons as particles. Electrons, however, like light, were part of electromagnetic radiation, and radiation was generally understood to be a wave phenomenon. In 1924, the French physicist Prince Louis de Broglie (1892-1987), influenced by Einstein s work on the photoelectric effect, showed that electrons had both wave and particle aspects. Wave mechanics, an alternative approach to quantum physics, was soon developed, based on the wave equation formulated in 1926 by the Austrian-born Erwin Schrodinger (1887-1961). Quantum mechanics and wave mechanics turned out to be complementary and both were fruitful for an understanding of valence. 

Describe the photoelectric effect, and discnss how related paradoxes of classical physics were resolved by quantum mechanics (Section 4.4, Problems 23 and 24). 

Quantum mechanics represents one of the cornerstones of modem physics. Though there were a variety of different clues (such as the ultraviolet catastrophe associated with blackbody radiation, the low-temperature specific heats of solids, the photoelectric effect and the existence of discrete spectral lines) which each pointed towards quantum mechanics in its own way, we will focus on one of these threads, the so-called wave-particle duality, since this duality can at least point us in the direction of the Schrodinger equation. 

Planck s revolutionary idea about energy provided the basis for Einstein s explanation of the photoelectric effect in 1906 and for the Danish physicist Niels Bohr s atomic model of the hydrogen atom in 1913. Their success, in turn, lent support to Planck s theories, for which he received the Nobel Prize in physics in 1918. In the mid-1920s the combination of Planck s ideas about the particle-like nature of electromagnetic radiation and Erench physicist Louis de Broglie s hypothesis of the wavelike nature of electrons led to the formulation of quantum mechanics, which is still the accepted theory for the behavior of matter at atomic and subatomic levels. 

Classical mechanics was unable to explain certain phenomena black body radiation, the photoelectric effect, and the stability of atoms and molecules, as well as their spectra. Quantum mechanics, created mainly hy Werner Heisenberg and Erwin Schrddinger, explained these effects. The new mechanics was based on six postulates ... 

Early attempts by nineteenth-century physicists to understand atoms and molecules met with only limited success. By assuming that molecules behave like rebounding balls, physicists were able to predict and explain some familiar phenomena, such as the pressure exerted by a gas. However, this model could not account for a number of newly discovered phenomena, such as the photoelectric effect or the emission spectra of atoms. The early twentieth century brought the development of quantum mechanics and the realization that the behavior of atoms and molecules cannot be described by the physical laws that work so well for everyday objects. 

Albert Einstein (1879-1955). .. was a German-bom theoretical physicist who is mainly renowned for his special theory of relativity and its extension to the general theory of relativity. In addition to this, he worked on statistical mechanics and quantum theory and investigated the thermal properties of light. At the beginning of his scientific career he also set important landmarks for colloid science. This applies particularly to his explanation of Brownian motion, but is also valid for the calculation of suspension viscosity as well as his theory of critical opalescence. In 1921, he was given the Nobel Prize in Physics Tor his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect . 

---