PHYSICS PROJECT2015-2016

XII-ARAMJAS PUBLIC SCHOOL

BY- DEVANSH JAIN

LASER AS SECURITY ALARM

INDEX

CONTENT PAGE NO.ACKNOWLEDGEMENT 2CERTIFICATE 3WHAT IS LASER 4LASER PHYSICS 5-6LASER AS SECURITY ALARM 7LIGHT DEPENDENT RESISTANCE

8

TRANSISTOR AND APPLICATIONS

9-12

CIRCUIT DIAGRAM 13PROCEDURE AND OBSERVATION

14

USES 15SUMMARY 16BIBLIOGRAPHY 17

I would like to express my special thanks of gratitude to my teacher, MISS.

RENU A.KUMAR as well as lab assistant, UPENDER SHARMA who gave

me the golden opportunity to do this wonderful project on the topic: LASER

AS A SECURITY ALARM, which also helped me in doing a lot of Research

and I came to know about so many new things I am really thankful to them.

Secondly I would like to thank my parents and friends who helped me a lot in

finalizing this project within limited time frame.

ACKNOWLEDGEMENT

CERTIFICATEThis is to certify that the Physics Project: LASER LIGHT AS SECURITY

ALARM has been submitted by the candidate DEVANSH JAIN with ROLL

NO: for the class 12 Practical Examination Of Central Board of

Secondary Education IN THE YEAR 2015-2016. IT IS FURTHER CERTIFIED

THAT THIS PHYSICS PROJECT IS THE INDIVIDUAL WORK OF THE

CANDIDATE.

SIGNATURE DATE:

L.A.S.E.R stands for Light Amplification by Stimulated Emission of Radiation

A Laser is a device that emits light through a process of optical amplification based in the stimulated emission of electromagnetic radiation. A laser differs from other sources of light in that it emits light coherently. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers. Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum, i.e., they can emit a single color of light. Temporal coherence can be used to produce pulses of light as short as a femtosecond.

WHAT IS LASER?

Laser have many important applications. They are used in common consumer devices like optical disk drives, laser printers, and barcode scanners; fiber-optic and free-space optical communication; laser surgery and skin treatments; cutting and welding materials; military and law enforcement devices for marking targets and measuring range and speed. Laser lighting displays use laser light as an entertainment medium.

LASER PHYSICSElectrons and how they interact with electromagnetic fields are important

in our understanding of chemistry and physics.

STIMULATED EMISSION

In the classical view, the energy of an electron orbiting an atomic nucleus is larger for orbits further from the nucleus of an atom. However, quantum mechanical effects force electrons to take on discrete positions in orbitals. Thus, electrons are found in specific energy levels of an atom

When an electron absorbs energy either from light (photons) or heat (phonons), it receives that incident quantum of energy. But transitions are only allowed in between discrete energy levels such as the two shown above. This leads to emission lines and absorption lines.

An external electromagnetic field at a frequency associated with a transition can affect the quantum mechanical state of the atom. As the electron in the atom makes a transition between two stationary states (neither of which shows a dipole field), it enters a transition state which does have a dipole field, and which acts like a small electric dipole, and this dipole oscillates at a characteristic frequency. In response to the external electric field at this frequency, the probability of the atom entering this transition state is greatly increased. Thus, the rate of transitions between two stationary states is enhanced beyond that due to spontaneous emission. Such a transition to the higher state is called absorption, and it destroys an incident photon (the photon's energy goes into powering the increased energy of the higher state). A transition from the higher to a lower energy state, however, produces an additional photon; this is the process of stimulated emission.

When an electron is excited from a lower to a higher energy level, it will not stay that way forever. An electron in an excited state may decay to a lower energy state which is not occupied, according to a particular time constant characterizing that transition. When such an electron decays without external influence, emitting a photon, that is called "spontaneous emission". The phase associated with the photon that is emitted is random. A material with many atoms in such an excited state may thus result in radiation which is very spectrally limited (centered around one wavelength of light), but the individual photons would have no common phase relationship and would emanate in random directions. This is the mechanism of fluorescence and thermal emission.

MATERIALS REQUIRED

Printed Circuit Board(PCB)Connecting WiresTransistor 2N7000L.E.DBuzzer100Ω and 6.8kΩ Resistors9V BatteryLaser LightSoldering MachineSoldering Wire

LASER SECURITY ALARM

A photo resistor or light-dependent resistor (LDR) or photocell is a light-controlled variable resistor. The resistance of a photo resistor decreases with increasing incident light intensity; in other words, it exhibits photoconductivity. A photo resistor can be applied in light-sensitive detector circuits, and light- and dark-activated switching circuits.

LIGHT DEPENDENT RESISTANCE(LDR)

A photo resistor is made of a high resistance semiconductor. In the dark, a photo resistor can have a resistance as high as several megohms (MΩ), while in the light, a photo resistor can have a resistance as low as a few hundred ohms. If incident light on a photo resistor exceeds a certain frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electrons (and their hole partners) conduct electricity, thereby lowering resistance. The resistance range and sensitivity of a photo resistor can substantially differ among dissimilar devices. Moreover, unique photo resistors may react substantially differently to photons within certain wavelength bands.

A photoelectric device can be either intrinsic or extrinsic. An intrinsic semiconductor has its own charge carriers and is not an efficient semiconductor, for example, silicon. In intrinsic devices the only available electrons are in the valence band, and hence the photon must have enough energy to excite the electron across the entire bandgap. Extrinsic devices have impurities, also called dopants, added whose ground state energy is closer to the conduction band; since the electrons do not have as far to jump, lower energy photons (that is, longer wavelengths and lower frequencies) are sufficient to trigger the device. If a sample of silicon has some of its atoms replaced by phosphorus atoms (impurities), there will be extra electrons available for conduction. This is an example of an extrinsic semiconductor.

A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.

The transistor is the fundamental building block of modern electronic devices, and is ubiquitous in modern electronic systems. Following its development in 1947 by American physicists John Bardeen, Walter Brattain, and William Shockley, the transistor revolutionized the field of electronics, and paved the way for smaller and cheaper radios, calculators, and computers, among other things. The transistor is on the list of IEEE milestones in electronics, and the inventors were jointly awarded the 1956 Nobel Prize in Physics for their achievement.

TRANSISTORS

The common-emitter amplifier is designed so that a small change in voltage (Vin) changes the small current through the base of the transistor; the transistor's current amplification combined with the properties of the circuit mean that small swings in Vin produce large changes in Vout.

Various configurations of single transistor amplifier are possible, with some providing current gain, some voltage gain, and some both.

From mobile phones to televisions, vast numbers of products include amplifiers for sound reproduction, radio transmission, and signal processing. The first discrete-transistor audio amplifiers barely supplied a few hundred milliwatts, but power and audio fidelity gradually increased as better transistors became available and amplifier architecture evolved.

Modern transistor audio amplifiers of up to a few hundred watts are common and relatively inexpensive.

TRANSISTOR AS AN AMPLIFIER

The 2N7000 and BS170 are N-channel, enhancement-mode MOSFETs used for low-power switching applications. The two are nearly identical except that the leads are arranged differently and the current ratings are somewhat different; they are sometimes listed together on the same datasheet, along with other variants 2N7002, VQ1000J, and VQ1000P.

The 2N7000 is a widely available and popular part, often recommended as useful and common components to have around for hobbyist use, along with such other popular discrete semiconductors as the 1N4148 and 1N4001 series diodes; the 2N2222,2N3904, and 2N3906 bipolar junction transistors; and the IRF510 power MOSFET. The BS250P is "a good p-channel analog of the 2N7000.

TRANSISTOR 2N7000

Packaged in a TO-92 enclosure, both the 2N7000 and BS170 are 60 V devices, capable of switching 200 mA (2N7000) or 500 mA (BS170), with a maximum on-resistance of 5 Ω at 10 V Vgs.

The 2N7002 is a slightly higher resistance, lower current variant, in a TO-236 package, also known as "small outline transistor" SOT-23 surface-mount package, which is the most commonly used three-lead surface-mount package.

A typical use of these transistors is as a switch for moderate voltages and

currents, including as drivers for small lamps, motors, and relays. In switching

circuits, these FETs can be used much like bipolar junction transistors, but

have some advantages:

low threshold voltage means no gate bias required

high input impedance of the insulated gate means almost no gate current is

required

consequently no current-limiting resistor is required in the gate input

APPLICATIONS OF 2N7000

CIRCUIT DIAGRAM

PROCEDUREDraw the circuit on PCBAssemble all the parts as described in the circuit diagramFix all the elements in the circuits by connecting wires and soldering machine.Check all the connections and attach 9V battery to give power supply.Buzzer will start blowing and LED starts glowing.Laser light is allowed to fall on the LDR.As soon as the laser light falls on the LDR, Buzzer stops blowing.

OBSERVATIONSAs soon as the light from the laser falls on the LDR, the buzzer does not blow.

LASER SECURITY ALARM

Instead of L.E.D, we can use digital counter for counting the number of students entering in the school for refreshment purpose and also for attendance purpose.

It is Best used in night in banks for security purpose.

It can be used as counter in banks to count the number of notes in the bank.

It can be used for counting the number of people entering the building by placing it at the entrance of the gate.

USES OF LASER SECURITY ALARM

When the light level is high, the resistance of the LDR decreases and buzzer does not blow.

When the light level falls, the resistance if the LDR increase. As this resistance increases in relation to the other resistor, which has a fixed resistance, it causes the voltage dropped across the LDR to also increase. When this voltage is large enough it will cause the transistor to turn on.

SUMMARY

YOUTUBE

N.C.E.R.T PHYSICS CLASS 12

PHYSICS LAB MANUAL BOOK

GOOGLE

WIKIPEDIA

REFERENCE BOOKS

BIBLIOGRAPHY