FIRST PHYSICS EXPERIMENT REPORT

Date : Wednesday, 26 November 2014Assistant : Member : Ira Ukhtianingsih (G74110041) Yuliyanti (G74120009) Siti Rohaeni (G74120025) Gita Pratiwi (G74120037) Dinda Yuansa S(G74120058) Fitri Fauziah (G74120069)

PHYSICS DEPARTEMENTFACULTY OF MATHEMATIC AND NATURAL SCIENCEBOGOR AGRICULTURE UNIVERSITYBOGOR2014

LASER CHARACTERISTICS

PURPOSEObserve and demonstrate the characteristics of the laser beam divergence include the nature, coherence, and fokusabilitas.

EQUIPMENTPhotometer (OS-8020) - Diffraction Slits (OS-9165B)- 0.5 mW Laser (SE-9367) - -22mm F.L. Lens (OS-9131)- Optics Bench (OS-9103) - 18 mm F.L. Lens (OS-9132)- Linear Translator (OS-9104A) - 48 mm F.L. Lens (OS-9133)- Component Carrier (5) (OS-9107) - Viewing Screen (OS-9138)- Variable Diaphragm (OS-9117) - Aperture Mask (OS-9139)- Diffuser (OS-9120)

THEORYLaser hair removal has in recent years received wide clinical acceptance in both medical and aesthetics settings, because of its long-term results, non-invasive nature, minimal treatment discomfort, and the speed and ease with which procedures can be performed [1] .Lasers have many important applications. They are used in common consumer devices such as optical disk drives, laser printers, and barcode scanners. Lasers are used for both fiber-optic and free-space optical communication. They are used in medicine for laser surgery and various skin treatments, and in industry for cutting and welding materials. They are used in military and law enforcement devices for marking targets and measuring range and speed. Laser lighting displays use laser light as an entertainment medium. [1] .

PROCEDURESa. Experiment 11) Position the laser on the optical bench and point the beam parallel to the optical bench.2) In a dark room, observe the color of the laser beam. Will appear very bright red color.3) Mark on a white paper with colored pens. Put -22 mm FL lens in front of the laser and color mark was observed when irradiated with laser light scatter (diverging). Measure the radius of the center of the first light.4) Move the lens. Observe the size of the image file at some distance from the laser is calculated per 10 cm to 100 cm. Measure the back fingers of each of the displacement distance.5) Repeat steps 1-4 again, but using a 18 mm lens FL.

b. Experiment 21) Position the laser on the optical bench and point the beam parallel to the optical bench.2) Attach resiever laser direction, and connect with measuring the intensity of light by using a multimeter. Measure the voltage !.3) Observe the laser and mark on a white paper with pen color.4) Vary the distance from the initial range of 0 to 100 cm, the initial distance is assumed as the minimum intensity of the laser light, then at a distance of 10 cm is the maximum intensity, minimum intensity of 20 cm, and 100 cm in turn.5) Each distance measuring fingers laser pattern on the paper and measure the voltage printed on the multimeter.

RESULTS

a. Experiment 1High lens (Y)(cm) Ordem

Distance Lens to Laser (l)(cm)Radius (d)(mm)

Long wave Laser (Experiment)105 (nm)Long wave Laser (Literature)(nm)

Concev

5

110420

633

2037.5

302.54.167

4022.5

501.81.8

601.51.25

701.20.857

8010.625

900.80.4

1000.50.25

b. Experiment 2Distance Lens to Lensa(cm)Intensity (Volt)

MaxMin

0-0.74

108.77-

20-8.80

308.75-

40-8.79

508.81-

60-8.80

708.79-

80-8.73

908.81-

100-8.82

One of characteristic laser is coherence, coherence is waves derived the same light source [2] . coherence in optics achived by divide the light from a single source into two or more beam of light, then can be combine to produce patterns interference [3] . The Coherence length can be used to measure the level of monochromatic a light source. Some applications requires a light source that has coherence time and coherence space eg for holography.Amplifiers and oscillators based on this principle are called LASER (Light Amplification by Stimulated Emission of Radiation) is a mechanism for emitting electromagnetic radiation, often visible light, via the process of stimulated emission. Coherence, monii chromaticity, collimation, spectral brightness and high intencity are main characteristics of laser light. Mechanism of laser action can be understood by considering the four processes depicted in,namely:pumping,spontaneous emission (fluorescence),stimulated emission and absorption. Laser generated from electron relaxation processes . At the time of this process , the number of photons will be in a different release a bunch of light flashlight laser emission occurs regularly , while the flashlight emission occurs at random . In the laser emission will produce light having a specific wavelength . different from the flashlight would generate light emission with wavelengths much . process that occurs is the electron in the state of the ground state ( the valence band ) got the status of energy then rises toward the conduction band ( excitation ) and then the electrons return to the initial state ( ground state ) followed by a few photons are separated . Then that energy carried large enough then it takes a resonator resonator can be either a lens or mirror that is often used is the lens and mirror . when in the resonator , the photons bounce against each other so that the resonator wall is strong enough to leave the resonator . lasers powerful enough to use as a cutting tool such is CO2.laser powerful laser is small diameter and high fotonnya energy [4] .Condition when amoun of atom in exitation condition it is called by populace inversion. In the past, somepeople suggest the way to get populace inversion was shining material by strong light. That way is called by optical pump. By that way, we as tough as pump electrons to rise from ground state condition to excitation condition. But, unfortunately that way didnt succeed because the electrons in excitation condition went down to ground state condition early. Now, the way people get populace inversion is by modifying optical pump. At beginning, electrons are pump to rise to A conditions. Arrive in A condition, electrons will shine/emission radiation spontaneously and go down to B condition (lower than A condition). In B condition, electrons will stuck till they get stimulation from light coming. In B condition is called metastable. The first electron which go down to ground state condition will stimulate another electron so it is called stimulate emissions.

SOURCE

[1] Goldberg D.J., Laser hair removal, Martin Dunitz, 2000. LASER HAIR. London : Martin Dunitz[2] Setyaningsih, Agustina.2006. Penentuan Nilai Panjang Koherensi Laser Menggunakan Interferometer Michelson. Semarang: Universitas Diponegoro.[3] Tipler, P.1991.Fisika Untuk Teknik dan Sains. Jakarta: Erlangga. [4] Nitish, Chhabra & Bhardwaj Sudeep. 2011. Laser-basic principle and classification. International Journal Of Reseach In Ayurveda & Pharmacy. Vol 2(1)132-141.