LAWS OF PHOTOELECTRIC EMISSION AND IT'S EXPLANATION IN SIMPLE WAY WITH HELP OF EINSTEIN'S EQUATION

LAWS OF PHOTOELECTRIC EMISSION

1. The photo current is directly proportional  to the intensity of light and is independent of frequency.
2. The kinetic energy of the photo electrons is directly proportional to frequency and is independent of intensity.
3. Photoelectric effect does not happens when the incident frequency is less than a minimum frequency ( threshold frequency )
4. There is no time lag between the incidence of photon and emission of electrons or photoelectric process is an instantaneous. 

Einstein's equation       

 EXPLANATION :

1. According to quantum theory each photon interacts only with  each electron. When the intensity is increases more photons will come and they will interacts with more electrons. This will increase the amount of photo current.
2. According to Einstein's equation  hvo  is constant  then kinetic energy is directly proportional to frequency.
3. We know Einstein's equation. If  v < vo , then kinetic energy becomes negative and it is impossible, in other words photoelectric effect does not happens.
4. According to quantum theory  each photon interact with each electron so different electrons will be interacted with different photons at same instant so there is no time lag between incidence and emission.

DATA COMMUNICATION DEVICES

We know that  inter networking  is the process of connecting two or more networks together so that data transmission between networks may take place. There is possibility that the networks, which are to be connected, are not compatible. In such cases of incompatibility of networks, it is required that a "black box" be inserted at the junction point so that necessary conversions are possible as data packet moves from one network to the other. Such a black box in general is called 'relay'. Relays may connect to or more networks. Bridges and gateways are examples of relays used for this purpose.



BRIDGE

A bridge is a device to link two networks. A bridge is used to link same type of networks (LANs). When a packet (data packet) reaches the bridge, it decides whether it is to be addressed to a node on the other side of the bridge or on the same side. A bridge filters out those packets which are addressed to the same side of the network and passes all other packets which are addressed to some  nodes on the other side of the network.


ROUTER

A router is similar in operation to a bridge, but it can connect two networks with different protocols.  A router may be connecting two networks A and B. A message originating from node 3 of network A may be directed to node 5 of network B. The router checks the node address and the network address and use algorithms to find the best path to reach the destination. Different networks may use different protocols for communication. Therefore some kind of mutual understanding is required for compatibility between the two protocols so that data can be transferred from one network to any other. A router is the device which establishes understanding between the protocols of different networks.


GATEWAY


A gateway is used to connect two networks of different types, it is like a router in the sense that it finds the optimal path for a message directed to a specific node in a different network. In addition, it can convert the message from one code to another. For example, it can convert an e-mail message received in one format into another.

VARIOUS NETWORK CONNECTORS

WHERE DO YOU CAN FIND THE REAL HAPPINESS.

I think all the people in this beautiful planet likes to lead a happy life. But due to different situations in life they couldn't find happy in their life. According to me the right place you can find the happiness is in jesus christ. He is the only one who can make you real happy. In the present world people search for happy and they find their answer in alcohol, drugs.  Doing bad things. Watching bad things etc. This is one of the big mistake that you makes in your life. You may think these things can make you happy but it's not the truth. It's not a joke because these items deliver only a temporary happy for few minutes, Few hours or for few days. After that you may be depressed or feel lonely by thinking that you have done this or that. You may loose your control and your total attitude may change. Another major problem of using drugs and alcohol is that people just start it for fun but later they get addicted to it. It causes lots and lots of problems so it's better to avoid such things. Just remember that these items can't give you the real happiness so as I told before the only place that you can find the real happiness is in jesus christ. So stay always close to him and I'm sure that he will let you to enjoy the real world of peace and happiness.

THE GOD IS GREAT. WE SHOULD LOVE HIM.

The God is great. He created such a beautiful planet earth for us. He provides us what we need. But the people are running to make money by forgetting the God almighty. In the journey of our life we have done many sins by knowing and unknowing but the god have forgiven our sins. He also remember us not to repeat the same mistakes. But what we do.? For our happiness we repeat the same mistakes . I think this  hurts God so we should try to avoid these kind of mistakes. We should love God has much as we could. It is the only way that we can enjoy the real happiness in our life.

PHOTOCELL, IT'S WORKING AND IT'S USES

A photocell is a technological application of the photoelectric effect. It is a device whose electrical properties are affected by light. It also some times called an electric eye. A photocell consists of a semi cylindrical photo sensitive metal plate c (emitter) and a wire loop A (collector) supported in an evacuated glass or quartz bulb. It is connected to the external circuit having a high tension battery B and micro ammeter as shown in the figure.

Sometime instead of the plate  C, a thin layer of photosensitive material is pasted on the inside of the bulb. A part of the bulb is left clean for the light to enter it. When light of suitable wavelength falls on the emitter C, photo electrons are emitted. These photo electrons are drawn to the collector A. Photo current of the order of a few micro ampere can be normally obtained from a photo cell.

A photocell converts a change in intensity of illumination into a change in photo current. This current can be used to operate control systems  and in light measuring devices. A photocell of lead  sulphide sensitive to infrared radiation is used in electric ignition circuits.

In scientific work, photo cells are used whenever it is necessary to measure the the intensity of light. Light meters in photographic cameras make use of photo cells to measure the intensity of incident light. The photocells, inserted in the door light electric circuit, are used as automatic door opener. A person approaching a doorway may interrupt a light beam which is incident on a photocell. The abrupt change id photo current may be used to start a motor which opens the door or rings an alarm. They are used in the control of a counting devices which records every interruption of the light beam caused by a person or object passing across the beam. So photocells help count the person entering an auditorium, provided they enter the hall one by one. They are used for detection of traffic law defaulters: an alarm may be surrounded whenever a beam of (invisible) radiation is intercepted.

In burglar alarm, (invisible) ultraviolet light is continuously  made to fall on a photocell installed at the door. A person entering the door interrupts the beam falling on the photocell. The abrupt change is photo current is used to start  an electric bell ringing. In fire alarm, a number of photocells are installed at suitable places in a building. In the event of breaking out of fire, light radiations fall upon the photocell. This completes the electric circuit through an electric bell or a siren which starts operating as a warning signal.

Photocells are used in the reproduction of sound in motion pictures and in television camera for scanning and telecasting scenes. They are used in industries for detecting minor flaws or holes in metal sheets. 

PARTICLE MODEL OF LIGHT

P a R T i C l E    M o d E l    o F     L i G H t 

Newton's fundamental contributions to mathematics, mechanics, and gravitation often blind us to his deep experimental and theoretical study of light. He made pioneering contributions in the field of optics. He further developed the corpuscular model of light proposed by Descartes. It presumes that light energy is concentrated in tiny particles called corpuscles. He further assumed that corpuscles of light were mass less elastic particles. With his understanding of mechanics, he could come up with a simple model of reflection and refraction. It is a common observation that a ball bouncing from a smooth plane surface obeys the laws of reflection. When this is an elastic  collision, the magnitude of the velocity  remains the same. As the surface is smooth, there is no force acting parallel to the surface, so the component of momentum in this direction also remains the same. Only the component perpendicular to the surface, i.e., the normal component of the momentum, gets reversed in reflection. Newton argued that smooth surfaces like mirrors reflect the corpuscles in a similar manner.

In order to explain the phenomena of refraction. newton postulated that the speed of the corpuscles was greater in water or glass than in air. How ever, later on it was discovered that the speed of light is less in water or glass than in air.

In the field of optics, Newton the experimenter, was greater than Newton the theorist. He himself observed many phenomena, which were difficult to understand in terms of particle nature of light. For example, the colours observed due to a thin film of oil on water. Properly of partial reflection of light is yet another such example. Everyone who looked into the water in a pond sees image of the face in it, but also sees the bottom of the pond. Newton argued that some of the corpuscles, which fall on the water, get reflected and some get transmitted. But the property could distinguish these two kinds of corpuscles ? Newton had to postulate some kind of unpredictable, chance phenomenon, which decided whether an individual corpuscle would be reflected or not. in explaining other phenomena, how ever, the corpuscles were presumed to behave as if they are identical, Such a dilemma does not occur in the wave picture of light. An incoming wave can be divided into two weaker waves at the boundary between air and water.

HISTORICAL NOTE OF DETERMINANTS

The Chinese method of representing the coefficients of the unknown of several linear equations by using rods on a calculating board naturally led to the discovery of simple method of elimination. the arrangement of rods was precisely that of the numbers is determinants. the Chinese, therefore early developed the idea of subtracting   columns and rows as in simplification of a determinant 'Mikami, China, pp 30, 93.

Seki Kowa, the greatest of the Japanese Mathematicians of seventeenth century in his work 'Kai Fukudai no Ho'  in 1683 showed that he had the idea of determinants and of their expansion. But he used this device only in eliminating a quantity from two equations and not  directly in the solution of a set of simultaneous linear equations. 'T. Hayashi, " The Fakudoi and Determinants in Japanese Mathematics," in the proc. of the Tokyo Math. Soc., V,

Vendermonde  was the first to recognize determinants as independent functions. He may be called the formal founder. Laplace (1772), gave general method of expanding a determinant in terms of its complementary minors. In 1773 Lagrange treated determinants of the second and third orders and used them for purpose other than the solution of equations. In 1801, Gauss used determinants in his theory of numbers.


The next contributor was Jacques-Philippe- Marie Binet (1812) who stated the theorem relating to the product of two matrices of m-columns and n-rows, which for the special case of m=n reduces to the multiplication theorem more satisfactory then Binet's 

The greatest contributor to the theory was Carl Gustav Jacob Jacobi, after this the word determinats received its final acceptance.