K. Sofjan Firdausi
Jurusan Fisika, Fakultas Sains dan Matematika, Universitas Diponegoro Semarang
Articles
35
Documents
Studi Efek Elektrooptis Pada Minyak Goreng

BERKALA FISIKA Vol 12, No 2 (2009): Berkala Fisika
Publisher : BERKALA FISIKA

Show Abstract | Original Source | Check in Google Scholar | Full PDF (191.461 KB)

Abstract

The aim of this research is to study differences between fresh palm oil and heated palm oil in the external static electric field. The external electric field used at this research was resulted from two parallel plates of 5 × 3 cm, separated by 2.5 cm and applied by high voltage from 0 to 11 kV. Light sources used here were red laser pointer (= 650 nm) and green laser pointer (= 532 nm) to measure change of polarization angle. The heated oil used here was fresh oil that was heated in circa 16 minutes. The results indicate that fresh oil has less average gradient of electro optic polarization (h) than heated oil, both of 650 nm and 532 nm. Theh’s value is measured more significant for = 532 nm than= 650 nm, and moreover can be used to measure the quality of oils based on fresh or polluted oil.        Keywords: palm oil, electrooptic, polarization.

PENGARUH FAKTOR EKSPOSI PADA PEMERIKASAAN ABDOMEN TERHADAP KUALITAS RADIOGRAF DAN PAPARAN RADIASI MENGGUNAKAN COMPUTED RADIOGRAPHY

BERKALA FISIKA Vol 11, No 4 (2008): Berkala Fisika
Publisher : BERKALA FISIKA

Show Abstract | Original Source | Check in Google Scholar | Full PDF (350.6 KB)

Abstract

It has been researched about the change of exposure factors in radiographic examination of abdomen to radiographic quality and radiation exposure using computed radiography. The change of exposure factors to radiographic quality is obtained by measurement of radiographic density, which transmitted to step wedges and phantom abdomen. The density difference of step wedge and abdomen at each change of exposure factors result in radiographic contrast. To obtain radiation dose for patients, it is accounted by analytic method. The affect of scattering rate dose is obtained by measurement of scattering exposure rate using survey meter with positioned 100 cm from the object. The result of experiment shows that change of exposure factors in radiographic examination of abdomen makes no significant difference between radiographic density and contrast; however, it has decreased the patient dose. Keywords: radiation exposure, radiographic density and contrast

Sifat Optis Tak-Linear Pada Material KDP

BERKALA FISIKA Vol 11, No 3 (2008): Berkala Fisika
Publisher : BERKALA FISIKA

Show Abstract | Original Source | Check in Google Scholar | Full PDF (268.939 KB)

Abstract

Non-linier optical properties of transparent material Kalium Di- hydrogen Phosphate (KDP) have been identified under the influence of external magnetic fields at wavelength 632.8 nm and 532 nm by using Faraday Effect method. The external  magnetic fields used in this experiment is produced from coils with total turns of 810, wire diameter of 0,8 mm, and soft magnet core, and is flowed by maximum AC current 5 A. The magnitude of magnetic fields can be produced is 194.23 mT. The optical property measured here is rotation of polarization angle ß of the laser beam after passed the transparent material. From the experiment, it is obtained Verdet’s constant value for transparent material KDP is (12.60 ± 0.59) min/G-cm at  = 632.8 nm and (14.93 ± 0.73) min/G-cm at  = 532 nm.   Key words: non-linier optic, KDP, magnetic fields, polarization, Verdet’s constant

Studi Kualitas Minyak Goreng Dengan Parameter Viskositas Dan Indeks Bias

BERKALA FISIKA Vol 11, No 2 (2008): Berkala Fisika
Publisher : BERKALA FISIKA

Show Abstract | Original Source | Check in Google Scholar | Full PDF (187.731 KB)

Abstract

The aim of this research to investigate the quality of palm oil through its viscosity and refractive index before and after used. Viscosimeter Ostwald is used to measure the viscosity and refractive method in prism is used to measure refractive index. The measurement was carried out in room temperature. The samples are fresh oil, and expired oil. Analysis of the quality of palm oil based on viscosity measurement and refractive index show that palm oil that had not been used is the highest value and the palm oil that twice used is the lowest value. Keyword: viscosity, quality of oil

Studi Pengaruh Medan Radio Frekuensi (RF) pada Minyak Goreng

BERKALA FISIKA Vol 11, No 1 (2008): Berkala Fisika
Publisher : BERKALA FISIKA

Show Abstract | Original Source | Check in Google Scholar | Full PDF (243.936 KB)

Abstract

A study of non linier optic has been carried out for palm oil induced by RF frequency field,e using white light and laser light. The e’s value is produced by RF generator with 2kV of voltage and in the range of frequency between 6.04 MHz and 11 MHz. In this research, he-ne laser with 632.8 nm of wavelength, green pointer laser with 532 nm of wavelength and white light of halogen with maximum power 130, are used as source of light. The physical characteristics observed in the experiment are change of light polarization that is transmitted through palm oil. From experiment result indicates that the change of polarization angle is not linearly dependent on e, At the same condition, the highest changes of polarization angle takes place when providing green laser, upright position of RF frequency field on polarization angle direction  900 for the twice used-palm oil. Keywords: non – linier optics, polarization angle, RF frequency field

Rancang Bangun Spektroskopi FTIR (Fourier Transform Infrared) untuk Penentuan Kualitas Susu Sapi

BERKALA FISIKA Vol 11, No 1 (2008): Berkala Fisika
Publisher : BERKALA FISIKA

Show Abstract | Original Source | Check in Google Scholar | Full PDF (262.566 KB)

Abstract

A Fourier Transform Infrared spectroscopy instrument has beed developed in the range middle infrared. The important instrument in this research is to make interferogram using He-Ne Laser based on Michelson interferometer. The result indicates that the interferogram seems work well and should give some spectra in the range of middle infrared frequencies. Key words: FTIR, interferogram, spectroscopy

Pengukuran Panjang Koherensi Menggunakan Interferometer Michelson

BERKALA FISIKA Vol 10, No 4 (2007): Berkala Fisika
Publisher : BERKALA FISIKA

Show Abstract | Original Source | Check in Google Scholar | Full PDF (391.483 KB)

Abstract

A simple measurement of coherence length of He-Ne laser, red diode laser, and green diode laser using Michelson interferometer has been conducted. The steps in this research were setting up the Interferometer by places movable mirror on mirror rail. To determine the coherence length of the laser’s light, movable mirror has been shifted until the interference fringes disappear on the screen. Results of measurement for the coherence length of He-Ne laser I is  cm, He-Ne laser II is  cm, red diode laser I is cm, and green diode laser II is  cm. Keywords: Coherence, coherence length.

Pengukuran Nilai  dan  Larutan Gliserin Terimbas pada Frekuensi PLN

BERKALA FISIKA Vol 10, No 4 (2007): Berkala Fisika
Publisher : BERKALA FISIKA

Show Abstract | Original Source | Check in Google Scholar | Full PDF (274.162 KB)

Abstract

The magnetooptical specific rotary power h and frequence specific rotary power z have been measured in the glycerine through the interaction between external magnetic field modulated at 50-60 Hz and modulated laser light at the wavelength of 632,8 nm and 532 nm. The sample induced by the magnetic field that has the maximum value of 170 mT. The source of light of 632,8 nm and 532 nm is modulated between 30 Hz and 100 Hz. The result of experiment indicates that values of h and z at l = 632,8 nm are more dominant than at l = 532 nm.    Key words: magnetooptic, specific rotary power, resonance frequency

Studi Interferometer Fabry-Perot Untuk Pengukuran Panjang Gelombang Cahaya

BERKALA FISIKA Vol 10, No 4 (2007): Berkala Fisika
Publisher : BERKALA FISIKA

Show Abstract | Original Source | Check in Google Scholar | Full PDF (206.813 KB)

Abstract

In this experiment, an interferometer Fabry-Perot method has been used to measure wavelength of diode laser. The first step is to calibrate the micrometer displacement using He-Ne laser in order to measure the diode and He-Ne wavelength. By shifting movable mirror, the transition of interference fringe in counted against the displacement of movable mirror. For the result of measurement, it is obtained for the wavelength of the red diode laser of, and green diode laser of.   Key word: Interferometer Fabry Perot, multiple beam interference.

Penentuan Koefisien Linier Elektro Optis Pada Aquades dan Air Suling Menggunakan Gelombang RF

BERKALA FISIKA Vol 10, No 4 (2007): Berkala Fisika
Publisher : BERKALA FISIKA

Show Abstract | Original Source | Check in Google Scholar | Full PDF (272.118 KB)

Abstract

The coefficients of electrooptics for water and refinery water in RF field have been determined. The RF frequency range used in the research is 6,04 MHz to 11 MHz. Two different light beam (532 nm and 632,8 nm) have been used to measure the change of light polarization after transmitted the samples. The result indicates that the linear and quadratic electro optic coefficients appear in the range of frequency-field. The refinery water has greater value of linear electro optic coefficient than aquades. It is also obtained that the greatest change of polarization angle take place when using the green laser in the field’s position of upright against the RF frequency field and polarization angle of 900.   Keywords: RF field, polarization angle, linear electro optic coefficient.