Collimated light

Collimated light is light whose rays are parallel, and therefore will spread minimally as it propagates. The word is related to "collinear" and implies light that does not disperse with distance (ideally), or that will disperse minimally (in reality). A perfectly collimated beam with no divergence cannot be created due to diffraction, but light can be approximately collimated by a number of processes, for instance by means of a collimator. Collimated light is sometimes said to be focused at infinity. Thus as the distance from a point source increases, the spherical wavefronts become flatter and closer to plane waves, which are perfectly collimated.
The word "collimate" comes from the Latin verb collimare, which originated in a misreading of collineare, "to direct in a straight line"

Laser light from gas or crystal lasers is highly collimated because it is formed in an optical cavity between two parallel mirrors, in addition to being coherent. In practice, gas lasers use slightly concave mirrors, otherwise the power output would be unstable due to mirror non-parallelism from thermal and mechanical stresses. The divergence of high-quality laser beams is commonly less than 1 milliradian, and can be much less for large-diameter beams. Laser diodes emit less-collimated light due to their short cavity, and therefore higher collimation requires a collimating lens.

 

Why deep diver take oxygen mixed with helium instead of pure oxygen while going deep in sea for respiration?

Answer:

To breathe underwater a diver must be supplied air at a pressure equal to that of the water surrounding the diver.

However there is an upper limit of oxygen pressure above which the oxygen becomes biochemically toxic.

Therefore, it is necessary to include something to dilute the oxygen in a diver's breathing gas. To satisfy normal breathing requirements at high pressures, it is necessary to supply between 0.2 and 1.5 atmospheres of oxygen with the rest of the balance made up by a non-toxic diluent (such as nitrogen).

Air of course is a suitable breathing mixture for a diver based primarily on nitrogen as the oxygen diluent.Air is in fact the preferred breathing mixture for all dives to depths of less than about 150-200 fsw (feet of sea water).

However, even at 150 fsw, when breathing air most divers feel the effects of nitrogen narcosis.

Beyond this depth helium is preferred as the diluent and is in fact particularly well suited to the depth range immediately beyond air diving (e.g., 150-250 fsw). Helium does not cause narcosis at these pressures, is relatively inexpensive and is readily available. Moreover helium has a low density and is, therefore, easy to breathe at such pressures.

There are problems with helium though, problems that are seriously amplified as diving depths approach those of the outer continental shelves and beyond.

First there is the problem of communication. Everyone knows what breathing helium will do to your voice. Due principally, it is believed, to changes in the speed of sound in the gas medium, this effect is a sensitive function of depth. Helium speech at sea level is distorted, in a way that seems funny to both the listener and the speaker, but it is completely intelligible. At 200 fsw speech with Helium is still reasonably understandable.

However, as depths increase to the range between 400 and 600 fsw the situation becomes more serious, and to someone trying to get a job done helium speech is no longer considered funny. Speech in this range is totally lost on an untrained ear, though anticipated statements can be understood by a listener familiar with the voice and the situation.

So often, however, a sudden change in the topic of conversation throws everyone off, and it is necessary for the diver to speak slowly, repeat himself and to try to say things a different way. It can be done but it is slow and consequently expensive.

The other problem is that Helium is about 4 times as good at conducting heat as nitrogen. Which when at the chilly depth of 500 fsw means that you are going to get VERY cold.

Reading a Capacitor's Value

Reading a Capacitor's Value

• Capacitor codes are similar to resistor codes. But with capacitors, the numbers are usually printed on the component, so you don't have to remember which colors stand for which numbers.
• Usually, a capacitor's nominal value in picofarads (pF) is indicated by three numbers on the capacitor's body.
  • The first two numbers represent the first and second digits of the nominal value. The third number represents the number of zeroes following those first two digits.
  • Example: If a capacitor's numeric code is 472, then the nominal value is 4700 pF, which is the same as 4.7 nF.

    
    

    Capacitor Tolerance Codes

    • Often the numeric code on a capacitor will be followed by a letter that indicates the capacitor's tolerance rating. Here are the tolerance letters that you'll see most often:
      

      Letter	Tolerance Rating
      F	±1%
      G	±2%
      J	±5%
      K	±10%
      M	±20%

Resistor Color Code

Resistor Color Code

• Usually, a resistor's value in ohms is indicated by several colored bands on the resistor's body.
• Each integer from 0 to 9 is represented by a color. The table below shows which colors represent these integers.

Integer	Color
0	Black
1	Brown
2	Red
3	Orange
4	Yellow
5	Green
6	Blue
7	Violet
8	Gray
9	White

• Two other colors (silver and gold) are also part of the resistor color code, but they have special meanings. Instead of simply representing numbers, these two colors represent tolerances ratings. In particular, gold represents a 5% tolerance, and silver represents a 10% tolerance. We often write this as ±5% or ±10%. (The expression ±5% is read as "plus or minus five percent." Similarly, ±10% is read as "plus or minus ten percent.") Finally, a tolerance of ±20% is represented by no colored band at all. 

Tolerance	Color
±5%	Gold
±10%	Silver
±20%	None

Reading a Resistor's Value

• Now that you know what the individual colored bands stand for, let's see how to put them all together to find a resistor's value.
• Usually, a resistor's value in ohms is indicated by four colored bands on the resistor's body.
• The first three bands of the color code give the resistor's nominal value.
  • The first two colored bands represent the first and second digits of the nominal value. The third band represents the number of zeroes following those first two digits.
  • Example: If the first three bands are yellow-violet-red, then the nominal value is 4700 ohms, or 4.7 kilohms. That's because yellow stands for 4, violet stands for 7, and red stands for 2. (So the red band tells you to add two zeroes after the 4 and the 7.)
• The fourth band (or tolerance band), gives the percentage variation from the nominal value that the actual resistance may have.
  • Example: If the four bands are yellow-violet-red-gold, then we saw above that the nominal value is 4700 Ω, or 4.7 kΩ. But you would not expect the resistor's actual value to be exactly 4700 Ω. It might actually be a bit higher or lower. The gold band is the manufacturer's way of assuring you that the actual value lies within 5% of the nominal value.

Active and Passive component

ACTIVE components increase the power of a signal and must be supplied with the signal and a source of power.Examples are bipolar transistors, field effect transistors etc. The signal is fed into one connection of the active device and the amplified version taken from another connection. In a transistor, the signal can be applied to the base connection and the amplified version taken from the collector. The source of power is usually a dc voltage from a battery or power supply. PASSIVE components do not increase the power of a signal. They often cause power to be lost. Some can increase the voltage at the expense of current, so overall there is a loss of power. Resistors, capacitors, inductors and diodes are examples of passive components. Integrated circuits contain both active and passive components. Since they usually increase the power of a signal and require a source of dc power they are treated as active devices.

Quiz question set 1

1        

         Who are the beneficiaries of TAPI pipeline?

    Ans-  Turkmenistan, Afghanistan, Pakistan and India

2       President of the World Bank……

   Ans-   Jim Yong Kim

3       The country which ranks second in terms of land area?

   Ans-  Canada

4       The first president of Bangladesh was

    Ans-  Sheikh mujibur rahman

5       The country that accounts for nearly 1/3 of the total teak production of the world is

   Ans- Myanmar

6       What does HTML stands for

   Ans- Hyper text mark up language

7       Which is the odd word out queen, king, pawn, bishop, cardinal, castle, ?

   Ans-  Cardinal all the rests are pieces of chess

8       What is the worlds smallest bird ?

   Ans-  Bee Huming bird(2 inch)

9      Which nation gave women the right to vote first ?

  Ans-  New Zealand

1      Who was the goddess of Love in Roman Myth?

  Ans-  Aphrodite

1     What is the Chemical Symbol for Iron?

Ans- Fe

      The name given to the border which separates Afghanisthan and Pakistan

Ans- Durand line.

Name of the living places of animals....

• Ant - Hill or Formicary 
  Badger - Sett 
  Bat - Roost, Cave 
  Bear - Den 
  Beaver - Lodge 
  Bee - Hive 
  Bird - Nest 
  Bird of Prey - Eyrie 
  Cat - Cattery, Lair, Den 
  Cattle - Barn, Byre, Pasture, Stable 
  Chicken - Coop, Run 
  Dog - Kennel 
  Fox - Earth, Den, Hole, Lair 
  Hare - Form 
  Horse - Paddock, Stable, Stall, Stud 
  Lion - Den 
  Mole - Burrow, Fortress, Tunnel 
  Otter - Holt, Ledge 
  Pig - Pen, Sty 
  Rabbit - Warren, Burrow, Cony-garth, Hutch 
  Sheep - Fold, Pen 
  Snake - Nest 
  Spider - Web 
  Squirrel - Drey 
  Termite - Mound 
  Tiger - Lair 
  Wasp - Nest, Vespiary 
  Wolf - Lair, Den

Goya Awards......

The Goya Awards, known in Spanish as los Premios Goya, are Spain's main national film awards, considered by many in Spain, and internationally, to be the Spanish equivalent of the American Academy Awards.

The awards were established in 1987, a year after the founding of the Academia de las Artes y las Ciencias Cinematográficas de España (Spanish Academy of Cinematic Art and Science), and the first awards ceremony took place on March 16, 1987 at the Teatro Lope de Vega, Madrid. The ceremony continues to take place annually around the end of January, and awards are given to films produced during the previous year.

The award itself is a small bronze bust of Francisco de Goya created by the sculptor José Luis Fernández.

Award ceremonies

The following is a listing of all Goya Awards ceremonies since 1986

Ceremony	Date	Best Picture winner
1st Goya Awards	March 17, 1987	Voyage to Nowhere
2nd Goya Awards	March 22, 1988	The Living Forest
3rd Goya Awards	March 21, 1989	Women on the Verge of a Nervous Breakdown
4th Goya Awards	March 10, 1990	Esquilache
5th Goya Awards	February 16, 1991	Tie Me Up! Tie Me Down!
6th Goya Awards	March 7, 1992	The Dumbfounded King
7th Goya Awards	March 13, 1993	Belle Époque
8th Goya Awards	January 21, 1994	Kika
9th Goya Awards	January 21, 1995	Running Out of Time
10th Goya Awards	January 25, 1996	The Day of the Beast
11th Goya Awards	January 25, 1997	The Dog in the Manager
12th Goya Awards	January 31, 1998	Secrets of the Heart
13th Goya Awards	January 23, 1999	The Girl of Your Dreams
14th Goya Awards	January 29, 2000	All About My Mother
15th Goya Awards	February 3, 2001	Pellet
16th Goya Awards	February 2, 2002	The Others
17th Goya Awards	February 1, 2003	Mondays in the Sun
18th Goya Awards	January 31, 2004	Take My Eyes
19th Goya Awards	January 30, 2005	The Sea Inside
20th Goya Awards	January 29, 2006	The secret life of words
21st Goya Awards	January 28, 2007	Volver
22nd Goya Awards	February 3, 2008	Solitary fragments
23rd Goya Awards	February 1, 2009	Camino
24th Goya Awards	February 14, 2010	Cell 211
25th Goya Awards	February 13, 2011	Black bread
26th Goya Awards	February 19, 2012	No Rest for the Wicked