Analysis Students' Misconception in Optical Material Using Three Tier Multiple Choice Diagnostic Test

This study aims to analyze the misconceptions of Senior High School students and their cause in Optical material. The data collection techniques used in this research are tests and interviews. The three tiers multiple-choice diagnostic test used consists of three levels, the first is a question, the second is the reason for the answer, and the third is the student's confidence level. The data analysis techniques used in this research are multiple-choice scoring analysis without fining and student's misconceptions level's percentage analysis. The lowest misconception level is 10.4% on the light refraction indicator, and the highest is 41.6% on the distance and characteristic of the image on the concave mirror. The sources of students' misconceptions found in this study are the students themselves, books, friends, teachers, students' daily experiences, and the Internet.

Orthogonal ray interferometer: modification for testing convex and concave mirror surfaces

A non-contact optical method for testing of large concave and convex mirrors both spherical and aspheric is presented. It is based on the orthogonal ray interferometer modification. The point source is placed near the testing mirror and the chief ray propagates normally to its axis. The information about a tangential profile of testing mirror is contained in an interference pattern that is a result of superposition between two wavefronts, the first is reflected from the mirror, the second bypasses the mirror. Testing of the entire surface is carried out by rotating the mirror. Interferogram decoding method and algorithm for determination of an error of the testing surface are presented. The proposed method does not require bulky additional optical components what differs it from existing methods and makes promising primary for testing large astronomical mirrors. Furthermore, the method is universal and suited for surfaces with various geometrical parameters. The scheme with some modification of the present method is applied for surfaces without axis of rotational symmetry or freeform surfaces.

Analysis of Interferometer with Micro-Mirror on Beam Splitting Cube

The control of the shape of the optical part surface by the interference method has become an integral part of the process of their shaping. With a precisely focused interferometer interferometry allows obtaining an interference pattern similar to a topographic map of the error profile of the wave surface under investigation. The interferometer must form a map of the optical surface with high accuracy --- the permissible distortion of the interference fringe caused by an interferometer error should not exceed 0.1 of the distortion value caused by an error on the examined surface. The dependence of the interference pattern formation on the errors in the arrangement of the interferometer components, i.e., defocusing, was theoretically analyzed using Fourier transforms. The analysis was performed for an interferometer containing a laser illuminator, a concave spherical mirror with a central hole, coaxial to the illuminator, and a beamsplitting element in the form of a cube-prism with a semitransparent hypotenuse face. On the first flat face of the cube-prism, a microspherical concave mirror is made with the center located on the optical axis of the interferometer. A method for calculating the defocusing of a controlled spherical mirror and the corresponding wave aberration of the working wavefront is presented. An example of calculating the design parameters of the interferometer and the permissible defocusing of the controlled spherical mirror is given

Determination of Potassium Levels in Bananas Using an Optical Sensor with a Flat and Concave Mirror Plane

Potassium is a nutrient that plays a role in maintaining the function of the muscles and nerves that control the heart and is needed for body stability. The potassium content in the body can be obtained from foods such as bananas. The development of instruments and methods that are developed to obtain a more accurate measurement of potassium concentration requires an instrument that has high linearity and sensitivity. The instrument is in the form of an optical sensor system equipped with the use of optical fibers to guide the waveform to maintain its intensity stability. In this study, an experimental method was conducted with a sample of a standard solution with potassium as the solute and pure water as the solvent. Then continue to measurements on samples of banana milk and green banana fruit extracts. The results of the analysis of the measurement data using an optical sensor with a concave mirror reflection plane obtained a sensitivity of 0.36 mV/ppm and a linearity of 82.56%. In the plane of the flat mirror reflection, obtained an optical sensor with a plane mirror reflection plane shows a sensitivity of 0.12 mV/ppm and a linearity of 97.6%. The highest and most accurate linearity value is found in the plane mirror plane results. The next stage is the result of the maximum output voltage read on the optical detector through an optical sensor with a sample of extracts of milk banana and green banana. The results of data analysis on the linear equation with the highest linearity obtained the potassium content in milk bananas of 391.54 ppm and the green banana extract solution obtained 307.91 ppm, so it can be concluded that the potassium content in milk bananas is higher than green bananas with a linearity of more than 97%.

Motionless Polarizing Structured Illumination Microscopy

In this investigation, we propose a motionless polarizing structured illumination microscopy as an axially sectioning and reflective-type device to measure the 3D surface profiles of specimens. Based on the spatial phase-shifting technique to obtain the visibility of the illumination pattern. Instead of using a grid, a Wollaston prism is used to generate the light pattern by the stable interference of two beams. As the polarization states of two beams are orthogonal with each other, a polarization pixelated CMOS camera can simultaneously obtain four phase-shifted patterns with the beams after passing through a quarter wave plate based on the spatial phase-shifting technique with polarization. In addition, a focus tunable lens is used to eliminate a mechanical moving part for the axial scanning of the specimen. In the experimental result, a step height sample and a concave mirror were measured with 0.05 µm and 0.2 mm repeatabilities of step height and the radius of curvature, respectively.

Measurements of Bicarbonate in Water Containing Ocean-Level Sulfate Using a Simple Multi-Pass Optical Raman System

The concentration of dissolved inorganic carbon in the oceans at depths of a few meters to thousands of meters is a critical parameter for understanding global warming. The concentration is both pH dependent and depth dependent. Current analysis that employs pH meters must account for several other parameters, such as salinity, temperature, pressure, and the dissolved carbon’s form, carbon dioxide, bicarbonate, or carbonate. Recently, Raman spectroscopy has been used to measure these forms directly in water at ~1000 ppm, which is unfortunately insufficient for typical ocean concentrations, such as ~115 ppm bicarbonate near the surface. Here, we employed a simple multi-pass optical system, a flat mirror to reflect the laser back through the sample, and a concave mirror opposite the entrance slit that effectively doubled the laser power and the collected Raman photons, respectively. This multi-pass optical Raman system with a 1.5 W, 532 nm laser was used to measure 30 ppm bicarbonate in water that contained 2650 ppm sulfate to simulate ocean water, a bicarbonate concentration well below that near the ocean surface. Furthermore, spectral analysis employed the bicarbonate C=O symmetric stretch at 1360 cm−1 instead of the C–OH stretch at 1015 cm−1 to avoid the intense, overlapping sulfate SO4 symmetric stretch at 985 cm−1. The calculated standard deviation of ~5 ppm for the described approach suggests that accurate measurement of bicarbonate in situ is possible, which has been, heretofore, either calculated based on pH or measured in a lab.