ASTR 170B2 Lecture Notes - Lecture 11: Bohr Radius, Cathode Ray, Electromagnetism
29 Sep 2018
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Astr ptys 170b2 - lecture 11 - structure and origin of matter. Historical ideas: democritus proposed matter is composed of indivisible particles of different shapes that make up basic elements: earth wind fire. John dalton argued atoms were solid, massy hard impenetrable. Jj thompson discovered that cathode rays are made of tiny particles called the electron. He was also able to determine the mass of them. Plum pudding model: electrons embedded in positive - positive particles are free. Rutherford experiment found matter is made of small positively charged particles. Rutherford"s atom: positively charged proton orbited by negatively charged electron. Found through sending alpha particles through a thin piece of gold foil. Some particles bounded back while most went through, proving most of the atoms are open space while there are small nuclei of. Rutherford-bohr atom: nucleus is composed of positively charged protons orbited by negatively charged electrons, held together by the electromagnetic force.
