Friday, 16 January 2015

Differences between Convex Lenses and Concave Lenses

The lenses are glassware or other transparent material having the ability to refract light, deflect light rays from an object and forming an image thereof. There concave and convex lenses.

1) Concave lens:

Diverging or concave lenses diverge the light beams incident in parallel on one of its face. These lenses have thinner central part edges. Light passing through a concave lens is deflected outwardly (diverges). Concave only produce virtual images, images that seem to come light rays. 

In this case it is a smaller image in front of the object (Clover). In the eyeglass, concave lenses make the eyes form a sharp image on the retina rather.

2) Convex Lens:

Convergent or Convex lenses makes the beams converge in the center and thicker than the edges. The main axis of the lens is an imaginary line perpendicular to the plane of the lens passing through its midpoint. It extends to both sides of the lens. Some distance from the lens along the main axis is the focal point (F)

Light rays impinging on a convex lens parallel to the main axis meet or converge at this point. The focal length of the lens depends both on how the refractive index of the material it is made of. A very important property of these lenses is that they produce real images.

Respiratory System


Breathing has two mechanisms,

The inspiration which supplies oxygen to the body and the expiry eliminating the CO2 
The term breathing also another direction where it meets the chemical oxidative reactions within the cells of the body; corresponding to oxygen consumption at the cellular level to degrade glucose or lipids and producing CO2;

The gas exchange in the alveoli is diffusion through a mechanism called the pulmonary ventilation matching. All respiratory movements ensuring the renewal of the air passing through the lungs. These movements are due to respiratory interring costal muscles and diaphragm (the muscle end to the base of the lungs that separates the chest from the abdomen).

Breathing is an automatic, unconscious phenomenon. At rest, the rate or respiratory rate of an average adult is 16 breaths per minute.

Every day an adult inspires 8000 liters of air (0.5 liters of air per breath about).
During inspiration, air enters the lungs via the nasal cavity and the trachea and the oxygen (O2) contained in the air passes through the wall of the alveoli. Its then binds directly into the blood capillaries on red blood cells (RBCs) and dissolved in blood plasma passes it in the opposite direction from the blood into the pulmonary air to be expelled by expiration.

Then the oxygenated blood is transported throughout the body (cells and organs) through the arteries by blood flow. In cells cellular respiration occurs when O2 is consumed and the CO2 produced by a redox reaction that releases energy in the form of a molecule called ATP. The CO2 produced is dissolved in blood plasma and is redirected to the lungs through the venous blood flow to be expelled into the pulmonary air by the expiration mechanism.

Dalton's Law of Partial Pressures


"If two or more then gases, chemically react with each other, in the same space, then at a constant temperature, the pressure of the mixture is equal to the addition of the pressures of each gas would have separately as it is only in that space used to be. "

P total = P.a + P.b + P.c + ... + Pn

In This formula:

  • is the total pressure of the mixture, also expressed as Ptot or just P
  • P.a or others are the partial pressure of gas "g", sometimes also expressed as PPG
  • Through n are the various gases in the gas mixture

Here we take as an example.

We keep it simple; air consists of 21% oxygen and 79% nitrogen, other gases we exclude.
Now we take three rigid, equal spaces and stop there the gas mixture, the proportion of oxygen and nitrogen in the share.

According to the law of Dalton the pressure of the mixture is equivalent to the sum of the pressures of the gases.

The pressure that would have one of the gases, as it would only occupy the space of the mixtures, we call the Partial Pressure.

From this follows:

Pg = Fg x P

In which:

  • Pg is partial pressure, expressed in bars
  • FGIS the fraction that the gas occupies in the mixture, expressed as a decimal (21% = 0.21)
  • P is the total pressure of the mixture, expressed in bar

Now we calculate the partial pressure of the oxygen in atmospheric air:

Fg x P = Pg
FO2 x P = PO2
0.21 x 1 = 0,21bar

Now we calculate the oxygen partial pressure of air at 35m depth:

FO2 x P = PO2
0.21 x 4.5 = 0.945 bar

Oxygen And its Characteristics


In its natural state Oxygen is an odorless, colorless, and tasteless gas. It is related to 16th group and 2nd period of periodic table, it’s a p block element [He] 2s22p4 with atomic number 8. 

The credit of discovering oxygen goes to three chemists: 

1) An Englishman, Joseph Priestley was 1st discoverer of oxygen, in 1774. He discovered it by focusing sun shine on to the mercuric oxide. 

2) A Swede, Carl Wilhelm Scheele founded oxygen in June 1771. Carl Wilhelm Scheele had written an article about his discovery but till 1777 it was not published.

3) A Frenchman, Antoine Lavoisier claimed that he had discovered oxygen gas.

Biological Role:

Oxygen firstly appeared on the Earth approximately 2 billion years ago in earth’s atmosphere, with the photosynthesis of blue & green algae. Oxygen gas is totally soluble in water, which makes the life in rivers, lakes & oceans possible.

Uses of Oxygen

The greatest official use of oxygen is in steel industries. Huge amount is also used in preparation of a huge number of chemicals along with nitric acid & hydrogen peroxide.

Oxygen is also used to make ethylene oxide, used as antifreeze & to make chloro ethane, and polyester, the manufacture to PVC. 
Oxygen is also used for cutting of metals and welding. A growth of use in the effluent from industry and the treatment of sewage.

Introduction to Computer Operating Systems


The operating system (Eng. Operating System or OS) is a set of programs responsible for the binding between the hardware resources of a computer and applications of the user. 

It provides computer startup and provides log-rise standardized interfaces for devices. There are SEVERAL operating systems: 
Windows, MS-DOS, Mac OS X, FreeBSD, Linux, Solaris, Palm OS, Symbian OS, 32 EPOC, etc.

The operating system provides many function utilities, file management, device management (through pilot) shared memory and CPU between the processes, etc. It provides many uses to this software through libraries.

The user can interact with the operating system or keyboard through an online interface to command or the mouse through a graphical interface.