Gambaran Pengetahuan Mahasiswa Tingkat Satu Diploma Tiga Refraksi Optisi Tentang Kelainan Refraksi

Eyes health is the most important thing in getting visual information to do daily activities. But visual disturbance or refraction disorders, experienced by many people and it cannot be ignored because they can disturb activities. Each people need to know about those kinds of refraction disorders. That way, it is expected that people can anticipate the symptoms of this refraction disorder. Knowledge of refraction disorder such as myopia, hypermetropy, and astigmatism is important for all people, especially for people who are steeped in the field of optical refraction. The purpose of this research is to know about refraction disorders knowledge of the first grade optition refraction students. The method that used in this research is descriptive quantitative, which the data from research sample is analyzed corresponding to statistic method that being used. While the instrument is questionnaire in the form of closed questions. The population is 54 regular university students majoring in optical refraction. Result of the research shows that 38% students in a good category, 44 % students are enough and the rest 18 % are in the poor category. Based on the result of the research, a solution is needed to improve students knowledge about optical refraction disorder.

Constraint-free wavelength conversion supported by giant optical refraction in a 3D perovskite supercrystal

Nonlinear response in a material increases with its index of refraction as n4. Commonly, n ~ 1 so that diffraction, dispersion, and chromatic walk-off limit nonlinear scattering. Ferroelectric crystals with a periodic 3D polarization structure overcome some of these constraints through versatile Cherenkov and quasi-phase-matching mechanisms. Three-dimensional self-structuring can also lead to a giant optical refraction. Here, we perform second-harmonic-generation experiments in KTN:Li in conditions of giant broadband refraction. Enhanced response causes wavelength conversion to occur in the form of bulk Cherenkov radiation without diffraction and chromatic walk-off, even in the presence of strong wave-vector mismatch and highly focused beams. The process occurs with a wide spectral acceptance of more than 100 nm in the near infrared spectrum, an ultra-wide angular acceptance of up to ±40∘, with no polarization selectivity, and can be tuned to allow bulk supercontinuum generation. Results pave the way to highly efficient and adaptable nonlinear optical devices with the promise of single-photon-to-single-photon nonlinear optics.

Net atomic charges, electric moments, and sign and magnitude of optical rotatory power in α-TeO2 at 296 K

Optical activity is determined from a point charge model in one enantiomorph of a chiral and semiconducting α-TeO2 crystal. Net atomic charges of Te and O atoms are iterated and electric moments derived. Second electric moments in the principal axis directions are calculated and their ratio is fitted by comparison with the corresponding ratio of the optical refraction indices. The components of the axial vectors are calculated and converted to the gyration tensor components. The optical rotatory power in the positive direction of the optic axis is determined, and the sense of optical rotation is defined from transformations of polar vectors of first rank of the TeO2 groups and visually confirmed in both enantiomorphs.

Dental Treatment of White Spots and a Description of the Technique and Digital Quantification of the Loss of Enamel Volume

The prevalence of white spots on teeth has increased in recent years. Regardless of their etiology, these lesions are characterized by a reduction in the enamel’s mineral phase, which is replaced by organic fluids. This causes an alteration of its chemical composition that affects its optical characteristics. Subsurface demineralization increases the pore volume of enamel, which in turn changes its optical refraction and results in the opaque color of white spot lesions. Here, we examined a non-invasive clinical technique used for eliminating these white spot lesions from enamel via two HCl-based products at different concentrations (6.6% and 15%). We used a digital method for evaluating the volumetric changes produced in dental enamel by the application of both products, one of which involved chemical erosion and the other, abrasive erosion. The mean volume of the enamel eliminated was −0.042 mm in 15% HCl, and −0.12 mm in 6.6% HCl. Thus, both 15% HCl and 6.6% HCl are capable of eroding the surface of the tooth enamel without reaching dentin. Moreover, 6.6% HCl produced a greater erosion of the dental enamel and left the surface a texture typical of an abrasive chemical-erosive product. The 15% HCl, however, produced an etching pattern typical of an erosive chemical with open enamel prisms prepared for subsequent adhesive procedures and restorers.

Correcting for physical distortions in visual stimuli improves reproducibility in zebrafish neuroscience

Optical refraction causes light to bend at interfaces between optical media. This phenomenon can significantly distort visual stimuli presented to aquatic animals in water, yet refraction has often been ignored in the design and interpretation of visual neuroscience experiments. Here we provide a computational tool that transforms between projected and received stimuli in order to detect and control these distortions. The tool considers the most commonly encountered interface geometry, and we show that this and other common configurations produce stereotyped distortions. By correcting these distortions, we reduced discrepancies in the literature concerning stimuli that evoke escape behavior, and we expect this tool will help reconcile other confusing aspects of the literature. This tool also aids experimental design, and we illustrate the dangers that uncorrected stimuli pose to receptive field mapping experiments.