This is a possible lesson plan for grade 12 physics of semiconductors:   1. Introduction: Review the concepts of conductors, insulators and semiconductors from class 11. Explain how semiconductors are used in various electronic devices such as diodes, transistors, LEDs, solar cells, etc. Show some examples of these devices and their applications. 2. Band theory of solids: Explain how the energy levels of electrons in solids form bands and gaps. Define the terms valence band, conduction band and forbidden gap. Explain how the band structure determines the electrical properties of solids. 3. Intrinsic and extrinsic semiconductors: Explain how pure semiconductors have very low conductivity at room temperature due to the small number of free electrons and holes. Explain how doping can increase the conductivity by creating impurity levels in the band gap. Define n-type and p-type semiconductors and their charge carriers. 4. PN junction: Explain how a PN junction is forme...

The development of atomic models is a fascinating story that spans over two millennia. It shows how human curiosity and scientific inquiry have led to a deeper understanding of the nature of matter and its structure. Here is a brief overview of some of the major milestones in this journey: - The Early Greeks Theory: The first atomic theorist was Democritus, a Greek scientist and philosopher who lived in the fifth century BC. He proposed that all matter was made of tiny, indivisible particles called atoms, which varied in shape and size. He also suggested that atoms moved in a void and combined in different ways to form different substances. - Dalton's Atomic Model: John Dalton developed the atomic theory around the 1800s. He based his model on experimental evidence and the law of conservation of mass. He stated that atoms were solid spheres that could not be broken down into anything simpler, that atoms of a given element were identical to each other, that atoms of different elemen...