Lasers and Optical Fibers: Principles and Applications
Lasers
Q1. Distinguish between spontaneous and stimulated emission of radiations (3 points). (3 Marks)
| Aspect | Spontaneous Emission | Stimulated Emission |
|---|---|---|
| Definition | Radiation emitted by an atom or molecule as it transitions from a higher energy state to a lower one, without external influence. | Radiation emitted when an external photon of appropriate energy interacts with an excited atom, causing it to release a photon identical to the incoming one. |
| Directionality | Emission is random and occurs in all directions, |
Galactic Structures and Universe Expansion: Key Insights
Structure of the Milky Way
Major Components
- Thin Disk: Contains most of the galaxy’s gas, dust, young stars, and active star formation (e.g., massive young stars in spiral arms).
- Thick Disk: Older stars, less gas and dust.
- Bulge: Dense cluster of old stars; includes the galactic center and possibly a bar structure.
- Halo: Sparse outer region containing ancient Population II stars and globular clusters; dominated by dark matter.
Challenges in Mapping
- The Sun’s position inside the galaxy obscures our view.
Relativistic Physics: Principles and Applications
Elements of Relativistic Physics
In 1905, Einstein published his Theory of Relativity concerning motion in inertial frames. In 1916, Einstein expanded his theory to include non-inertial systems and gravitation, naming it the “General Theory of Relativity.”
Relativity in Classical Mechanics
We know that the trajectory of a body depends on the observer. For example, consider a plane that drops an object:
- The pilot observes that the trajectory of the falling object is straight (reference system O’).
- However,
Understanding Energy: Types, Units, and Sources
Energy: Forms, Measurement, and Production
Types of Energy
- Electromagnetic Energy: Power manifested as radiation.
- Internal Energy: The sum of all energies less than that of the rest mass.
- Binding Energy or Chemical Energy: The energy that holds atoms and electricity together.
- Thermal Energy or Heat: Due to the motion of atoms and molecules, it is a form of kinetic energy.
- Nuclear Power: The energy contained in the nucleus of atoms; no more energy is rest mass.
Units of Energy Measurement
- Joule (J): The
Understanding LED Technology: Functionality and Advantages
LED Technology
A Light-Emitting Diode, also known as an LED, is a semiconductor device that emits incoherent light when a reduced spectrum is polarized directly through the PN junction, and an electric current circulates.
This phenomenon is a form of electroluminescence.
The color depends on the semiconductor material used in the construction of the diode and may vary from ultraviolet, through the visible spectrum, to infrared.
Light-emitting diodes that emit ultraviolet light are also called UV
Galilean and Newtonian Mechanics: A Historical Analysis
Galilean Mechanics: Challenging Aristotle’s Authority
Historians of science often credit Galileo Galilei as the first to study mechanics free of presuppositions, moving beyond Aristotelian frameworks.
Aristotle approached the problem of motion (or change) qualitatively. He developed a dual ontology, where the supralunar and terrestrial regions, composed of different elements, were governed by distinct physical laws. The supralunar region was thought to consist of the fifth element, ether, characterized
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