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Franck Condon Principle
The Franck–Condon principle is one of the most fundamental concepts in molecular spectroscopy, explaining why vibrational structures appear in electronic spectra of molecules and why certain transitions are more intense than others. When a molecule undergoes an electronic transition—whether by absorption or emission of radiation—the change in the electronic state occurs on a timescale much faster than nuclear motion. Electrons are extremely light compared to nuclei; therefore, their transitions happen almost instantaneously relative to the vibrational and rotational movement of the nuclei. As a consequence of this difference in timescales, the nuclei can be considered “frozen” during the electronic transition. This approximation is the core of the Franck–Condon principle and leads to a vertical transition between potential energy curves on a Born–Oppenheimer energy diagram.
Scattering: Partial Wave Analysis
Partial wave analysis is a fundamental method in quantum scattering theory used to analyze the interaction of a particle with a localized potential by exploiting the rotational symmetry of the problem. When a quantum particle of definite momentum is incident on a scattering center, its wavefunction far from the interaction region can be expressed as a superposition of an incoming plane wave and an outgoing spherical wave.
Chokes and Transformers
Chokes and transformers are fundamental electromagnetic components widely used in electrical and electronic systems, particularly in power supplies, communication circuits, and signal-conditioning networks. Both devices operate on the principles of electromagnetic induction and magnetic flux linkage, yet they serve distinct functional roles within circuits. A choke is essentially an inductor designed primarily to impede alternating current (AC) while allowing direct current (DC) to pass with minimal resistance. In contrast, a transformer is a static electrical device that transfers electrical energy between two or more circuits through mutual induction, usually with the purpose of changing voltage or current levels, or providing electrical isolation.
RF and AF Oscillators
Oscillators are fundamental electronic circuits capable of generating periodic waveforms without the need for an external input signal. They operate by converting direct current (DC) power into alternating current (AC) signals through the use of active devices such as transistors, operational amplifiers, or vacuum tubes, in conjunction with passive components like resistors, capacitors, and inductors. Depending on the frequency range of the generated signal, oscillators are broadly classified into Audio Frequency (AF) oscillators and Radio Frequency (RF) oscillators. AF oscillators typically generate signals in the range of approximately 20 Hz to 20 kHz, which corresponds to the human audible spectrum. These oscillators are widely used in audio signal generators, public address systems, audio testing equipment, and musical instruments. RF oscillators, on the other hand, operate at much higher frequencies, typically from hundreds of kilohertz to several gigahertz, and form the backbone of radio communication systems, including transmitters, receivers, radar, television broadcasting, and wireless communication technologies.
Capacitors
A capacitor is a fundamental passive electronic component used to store electrical energy in the form of an electric field. It consists essentially of two conducting surfaces (plates) separated by an insulating medium known as a dielectric. When a potential difference is applied across the plates, equal and opposite charges accumulate on them, giving rise to an electric field within the dielectric. The ability of a capacitor to store charge per unit potential difference is quantified by its capacitance, measured in farads (F). Capacitors are indispensable in both DC and AC circuits and play a crucial role in signal processing, power conditioning, filtering, timing, coupling, decoupling, and energy storage.
Breadboard Usage
A breadboard is one of the most fundamental and widely used tools in experimental electronics and applied physics laboratories, especially at the undergraduate and postgraduate levels. It serves as a temporary construction platform for prototyping, testing, and analyzing electronic circuits without the need for soldering. The term “breadboard” originates historically from early experimental setups where wooden boards (sometimes literally breadboards) were used to mount electronic components. Modern breadboards, however, are standardized plastic boards with internal metallic spring contacts arranged in a highly structured manner.
JET: English-Lecture-VI
Clock
JET: English-Lecture-V
Calendars
Practicals
PG Practicals
Road Map: SUSY
🔷 Where You Stand (Important)
Contour Integration
The basic idea of contour integration is to extend the concept of integration from the real line to the complex plane. Instead of integrating a function along a real interval, we integrate it along a path (or contour) in the complex plane. This allows us to use the properties of analytic functions and the residues of poles to evaluate integrals that would be difficult or impossible to compute using standard real analysis techniques.
JET: English-PRACTICE SET-I
PRACTICE SET-I
JET: English-Lecture-IV
Ratio
Quantum Mechanics in Momentum Space by M Lieber
By M. Lieber Received 18 June 1974
JET: English-Lecture-III
Time & Distance
Star & Delta Connection
Star (also called Wye or Y) and Delta (Δ) connections are fundamental network configurations used extensively in electrical engineering, circuit design, and power system analysis. These connections help simplify complex three-phase networks, making them easier to analyze for voltage, current, impedance, and power calculations. The star connection consists of three circuit elements whose one end is connected to a common junction known as the star point or neutral point, while the other ends form the three independent phase terminals. This configuration resembles the shape of the letter ‘Y’. It is widely used in power transmission systems, distribution networks, and balanced load connections due to its ability to provide two voltage levels—phase and line voltages.
PG-II-Practical
JET: English-Lecture-II
Number & Letter Series
Fock
On the Theory of the Hydrogen Atom
by V. Fock, Leningrad
(Received August 5, 1935)