Author: haroonkhan
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QUANTIZATION-THE CORE OF QUANTUM PHYSICS
Let’s quickly review the major problems faced by classical physics at the turn of the twentieth century: 1. Classical physics would predict that a blackbody should radiate an infinite amount of UV light. However, hot objects actually produce a limited glow that peaks at a wavelength dependent on temperature and then decays to zero at short…
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ORBITALS AND NOT ORBITS
In spite of its success with explaining the spectral lines produced by the hydrogen atom, Bohr’s atomic model is not perfect. It only works for atoms that have one electron. That is, it only applies to hydrogen, ionized helium (He+), doubly ionized lithium (Li++), and a few other light ions. More importantly, however, it does…
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BOHR’S SPARK OF GENIUS
Rydberg had been able to capture the observed periodicity of the hydrogen lines in an elegant formula, but he had no idea what underlying physical process could be responsible for such mathematical regularity. Returning to 1911, we find the world of physics was faced with a major riddle about the atomic structure proposed by Rutherford.…
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EMISSION SPECTROSCOPY
Let’s see those hydrogen lines for ourselves! We will use the kind of hydrogen “spectrum tube” available at any store that sells educational scientific supplies. Although they are all pretty much the same, their price varies quite a bit based on the store’s brand name. The least-expensive spectrum tubes are sold by Information Unlimited (under…
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Introduction
In this app last section left us with a planetary model of the atom that takes into account the existence of the nucleus, but which is inherently unstable. To recap, the model proposes that the centrifugal force of the revolving electron just exactly balances the attractive force of the nucleus. However, the issue is that…
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RUTHERFORD’S PLANETARY MODEL OF THE ATOM
Rutherford came up with a new model of the atom that accounted for his scattering results: he proposed that the positive charge and its associated mass is concentrated in the nucleus, and that the negatively charged electrons are orbiting around it, like planets. In his 1911 paper discussing the alpha-particle scattering results,20 Rutherford mentioned the planetary…
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RUTHERFORD’S ALPHA-SCATTERING EXPERIMENT
Meanwhile, Rutherford’s colleague Hans Geiger was exploring the use of thin films of mica—a transparent mineral that can be split into very thin slices—as radiation windows for his detector tubes. Geiger noticed that mica spread out a beam of alpha radiation by slightly deflecting some of its alpha particles. Together with Ernest Marsden—a young undergraduate…
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WHAT ARE ALPHA PARTICLES?
In 1909, Rutherford and his colleague Thomas Royds really wanted to know what made up alpha particles. They carried out many experiments with alpha particles emitted from radon—a gas that occurs naturally as the decay product of radium, and which often accumulates in basements to a point where it may pose health risks. The radon…
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THE IONIZING POWER OF ALPHA
The experiment on the penetrating power of radiation (Figure 62) could lead you to believe that alpha radiation is weak because it is so easily absorbed. However, the exact opposite is true. Alpha particles are so massive that they lose their energy by ripping atoms to pieces as they fly through matter. Eventually, alpha particles…
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THE NATURE OF BETA RADIATION
At the time, Rutherford had classified radiation based only on its penetrating power. However, he soon found that an electric or magnetic field could split such emissions into three types of beams. Based on the direction in which the rays were deflected, it was found that alpha rays carried a positive charge, beta rays carried…