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Laser Light : An Introduction
L A S E R S
Light Amplified by Stimulated Emission of Radiation i.e. LASER is one of the most incredible discoveries of Physics. First produced in 1960s, it recently completed its 50th year.
Laser light is emitted when atoms make transition from one Quantum State to a lower one.
Properties of Laser Light
1) Laser light is highly monochromatic.
2) Laser Light is highly coherent .
3) Laser light is highly directional.
4) Laser light can be sharply focused.
Types of Lasers
There are many kinds of LASERs differing their operational wavelength & applications:
I. Gas LASERs:
The Helium-Neon Gas Laser, Carbon dioxide gas Laser
II. Chemical LASERs:
HF Laser
III. Solid LASERs: Ruby LASER (most popular), Hybrid Silicon LASER, Diode LASER
IV. Metal Vapour LASERs: Copper Vapour LASER, Gold Vapour LASER
V. Dye LASERs
VI. RAMAN LASERs
VII. Free Electron LASER
VIII. Gas Dynamic LASER
Uses
* The smallest Lasers are use in Fibre Optics– for -Voice & Data Transmission over Optical Fibres.
* The Largest lasers are used for nuclear fusion research, to measure astronomical distances and in military applications.
* Other uses are– Reading Bar Codes, Manufacturing and Reading CDs and DVDs, Performing Surgery, Surveying, Cutting hundred layes Cloth at a time in the garment industry, weldings and in generating holograms.
Introduction to the Universe: Part II: Systems of Stars: Solar System and Our Sun
What does “The Solar System” mean?
The Solar System means the system of the Sun. All bodies under the gravitational influence of our local star, the Sun, together with the Sun, form the Solar System.
Bodies? What kind of bodies?
•The largest bodies, orbiting the Sun, including Earth are called planets.
•Often smaller cool bodies called satellites or moons, orbit a planet.
•Bodies smaller than than the planets that orbit the sun are classed as
asteroids if they are rocky or metallic, comets if they are mostly ice and dust, and meteoroids if they are very small. Most comets release gases as they near the heat of sun, producing a luminous cloud called coma & often a long tail. A meteoroid that burns in Earth’s atmosphere is a meteor, while one that reaches Earth without burning completely becomes a meteorite.
• After the exclusion of Pluto from the planet category, a new category is formed: Dwarf Planet.
Elements of Solar System:
Stars: (1) The Sun
Planets: (8) Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
Dwarf Planets: (4) Pluto, Charon, Eris, Ceres- along with the numerous satellites that travels around most of planets.
Others:
Asteroids
Interplanetary Dust
Plasma etc.
What’s Next?
In this article, I shall discuss about the Sun only. Further bodies will be discussed in Part IV & V. While, next Part i.e. PART III, will bring you into the interior of Sun. I suggest you again to read Part I of this Series. 
The Sun
SnapShots & facts about the Sun:
• Sun is one of more than 100 billion stars in the giant spiral galaxy called the Milky Way.
• Sun is the center of the solar system. Its mass is about 740 times as much as that of all the planets combined.
• It continuously gives off energy in several forms- visible light; invisible infrared, ultra-violet, X-rays and γ -rays, cosmic rays, radio waves and plasma.
•The Sun generally move in almost circular orbits around the galactic center at an average speed of about 250 km per second.
•It takes 250 million years to complete one revolution round the center. This period is called a Cosmic Year.
•It’s energy is generated by nuclear fusion in its interior. It is calculated that the Sun consumes about 4million tonnes of hydrogen every second. At this rate, it is expected to burn out its stock of hydrogen in about 5billion years and turn into a red giant.
Solar Statistics
Absolute Visual Magnitude: 4.75
Diameter: 1,384,000 km
Time of one Rotation as seen from the Earth: 25.38days (at equator) to 33days (at poles).
Chemical Composition:
Hydrogen 71%
Helium 26.5%
Other Elements 2.5%
Age: 4.5 billion years aprox.
Expected lifetime: 10 billion years aprox.
Mean distance from Earth 8.2 light seconds i.e. Aprox. 150 million km.
