Month: August 2023
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The Equivalence Principle & Black Holes
The equivalence principle is one of the laws of nature and it is connected with the nature of gravitation. In general relativity theory, the equivalence principle states that a gravitational field is locally equivalent to an accelerated frame. To be precise, it says that a freely falling observer or system will not experience the effects…
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The Limitations of Classical Physics
Light waves and other forms of electromagnetic waves travel through free space at the speed c = 3.0 x 108 m/s. The speed of light sets an upper limit for the speeds of particles, waves and the transmission of information. In our everyday experiences, we mostly deal with objects that move at speeds much less…
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What is a Black Hole?
A black hole can be described as an area of space where the gravity is so strong that nothing, including light or other electromagnetic waves has enough energy to escape it. In varied ways, a black hole acts like an ideal black body, as it reflects no light. Black holes are thought to form when…
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Spin Quantum Number
This property of atomic electrons was discovered through experimentation. The close observation of spectral lines revealed that each line was actually a pair of very closely-spaced lines, and what is referred to as fine structure was hypothesized to result from each electron “spinning” on an axis as if a planet. Electrons with different “spins” would…
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Bohr’s Correspondence Principle
Bohr’s correspondence principle states that predictions of quantum theory must correspond to the predictions of classical physics in the region of sizes where classical theory is known to hold. The classical sizes for length, mass, and time are on the order of centimeters, grams, and seconds and typically involve very large quantum numbers like can…
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Magnetic Quantum Number
The magnetic quantum number for an electron classifies which orientation its subshell shape is pointed. The “lobes” for subshells point in multiple directions. These different orientations are called orbitals. For the first subshell (s; l=0), which look like a sphere pointing in no “direction”, so there is only one orbital. For the second (p; l=1)…
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The Exclusion Principle
The exclusion principle states that no two electrons in an atom can have the same set of quantum numbers i.e. be in the same quantum state. Note, if this principle wasn’t valid, every electron would occupy the 1st atomic state (state of lowest energy), the chemical behaviour of the electrons would be significantly different and…
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Transmission Electron Microscope (TEM)
Electron beams are capable of providing crystallographic information about nanoparticle surfaces and can also be used to produce images of the surface, and they play this role in electron microscopes. The Operation of Transmission Electron Microscope In a transmission electron microscope the electrons from a source such as an electron gun enter the sample. They…
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Angular Momentum Quantum Number
A shell is made up of subshells. Subshells are regions of space where electron “clouds” are allowed to exist, and different subshells actually have different shapes. The first subshell is shaped like a sphere as illustrated in Fig 1.0(s) i.e. you can visualize it as a cloud of electrons surrounding the atomic nucleus in three…
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Einstein’s Special Theory of Relativity
Einstein special theory of relativity is based on two assumptions: The first proposition asserts that all the laws of physics, those dealing with electricity and magnetism, optics, mechanics, thermodynamics, etc. will have the same mathematical form or be covariant in all coordinate frames moving with constant velocity relative to one another. This postulate is a…