Analisis kemampuan represenasi matematis siswa MAN II Kota Batu pada materi deret geometri

The representation ability possessed by students is one of the key factors in learning mathematics in schools. Because it needs a study to understand how the ability of representation of students when given a problem. The purpose of this study is to describe the mathematical representation ability of students in class XI IPA MAN II Batu on geometrical series material. For this reason, the research conducted is a qualitative research with a descriptive approach so that researchers can describe how the students' representational abilities. Students are grouped in the ability category of high (KT), moderate (KS), and low (KR). The results of this study are KT, KS, and KR have not met the indicators of the ability of representation that has been determined. The non-fulfillment of these indicators is due to a mismatch between external representation and internal representation.

Photonic Wannier-Stark Ladder from Coupled Electromagnetic Cavities

We have investigated the photonic Wannier-Stark ladder in the system of coupled electromagnetic cavities, which consists of a stack of metallic plates structured with subwavelength apertures and where the tilted potential effect is mimicked by imposing the gradient variation of refractive index. Making an analogy to its quantum counterpart and assuming the translational property of its solutions, we have shown the photonic ladder has the eigenenergies, that is, frequencies, in a geometrical series. Within the approximation of small gradient, the ladder states manifest the equidistant frequency spacing in the spectrum. By both analytical derivation and numerical simulation, we have illustrated the geometrically progressed energies of the photonic Wannier-Stark ladder.

CHEMICAL STIMULATION BY ALCOHOLS IN THE BARNACLE, THE FROG AND PLANARIA

1. The stimulating efficiencies of some normal primary aliphatic alcohols have been determined for the barnacle, the frog, and Planaria, under conditions which do not involve narcosis or simultaneous stimulation by other agents. 2. Concentrations of the successive alcohols necessary to produce a given stimulatory effect vary according to the following geometrical series: 1: a–1: a–2: a–3: a–4: . . . ., where a represents some real number. 3. Within certain limits the relationship between the logarithm of the concentration necessary to produce a given effect and the reciprocal of the reaction time is linear in the frog and in Planaria. 4. The concentration effect may be expressed by an equation which contains one constant characteristic of the alcohol series, and another one characteristic of each member. The ratio of the latter constants for successive alcohols represents a in the above series. 5. The stimulation by alcohols in these animals is considered to be due to energy changes at the receptive surfaces, brought about by a definite orientation of the respective alcohol molecules. Increase in stimulating efficiency as the number of CH2 groups increase must be due to the rôle of the non-polar portion of the alcohol molecule, since the polar group remains practically constant throughout the series. 6. In homologous series of organic compounds it is conceived that stimulating effects will be produced either by the polar group or the non-polar group, according to which one becomes dominant in effect, or to a combination of the two.