CHEMISTRY GLOSSARY
Schellbach’s burette → Schellbachova bireta
When colourless liquids are used, parallax mistake is avoided by use of Schellbach’s burette. On the inside wall opposite to graduation scale it has a melted in ribbon from milky glass in the middle of which a blue line is found. The level of liquid is now spotted very easily because of light breaking in the meniscus blue line now looks like a double spike.
Snell’s law → Snellov zakon
When a light ray comes on a boundary between two transparent media, it will be partly reflected and partly refracted. Both rays, reflected and refracted ray, lay in the plane of incidence. The angle of reflection is equal to the angle of incidence. The angle of refraction (Θ2) is related to the angle of incidence (Θ1) via Snell’s law:
where n1 and n2 are dimensionless constants - indexes of refraction of the two media.
solar cell → sunčeva ćelija
Solar cell, or photovoltaic cell, is a device that captures sunlight and transforms it directly to electricity. All solar cells make use of photovoltaic effect, so often they are called photovoltaic cells. Almost all solar cells are built from solid-state semiconducting materials, and in the vast majority of these the semiconductor is silicon.
The photovoltaic effect involves the generation of mobile charge carriers-electrons and positively charged holes-by the absorption of a photon of light. This pair of charge carriers is produced when an electron in the highest filled electronic band of a semiconductor (the valence band) absorbs a photon of sufficient energy to promote it into the empty energy band (the conduction band). The excitation process can be induced only by a photon with an energy corresponding to the width of the energy gap that separates the valence and the conduction band. The creation of an electron-hole pair can be converted into the generation of an electrical current in a semiconductor junction device, wherein a layer of semiconducting material lies back to back with a layer of either a different semiconductor or a metal. In most photovoltaic cells, the junction is p-n junction, in which p-doped and n-doped semiconductors are married together. At the interface of the two, the predominance of positively charged carriers (holes) in the p-doped material and of negatively charged carriers (electrons) in the n-doped material sets up an electric field, which falls off to either side of the junction across a space-charge region. When absorption of a photon in this region generates an electron-hole pair, these charge carriers are driven in opposite directions by the electric field, i.e. away from the interface and toward the top and bottom of the two-layer structure, where metal electrodes on these faces collect the current. The electrode on the top layer (through which light is absorbed) is divided into strips so as not to obscure the semiconducting layers below. In most widely used commercial solar cells, the p-doped and n-doped semiconductive layers are formed within a monolithic piece of crystalline silicon. Silicon is able to absorb sunlight at those wavelengths at which it is most intense-from the near-infrared region (wavelengths of around 1200 nm) to the violet (around 350 nm).
spectrophotometer → spektrofotometar
Spectrophotometer is an instrument for measuring the amount of light absorbed by a sample.
The absorption of light by a substance in a solution can be described mathematically by the Beer-Lambert law
where A is the absorbance at a given wavelength of light, ε is the molar absorbtivity or extinction coefficient (L mol-1 cm-1), unique to each molecule and varying with wavelength, b is the length of light path through the sample (cm), and c is the concentration of the compound in solution (mol L-1).
visible radiation → vidljivo zračenje
Human eye can only see electromagnetic radiation of wavelengths form 400 nm to 760 nm. This narrow part of electromagnetic spectrum is called visible radiation. Visible (white) light is a mixture of light of all kind of colours, it can be separated, with the help of a glass prism, into its component colours - visible light spectrum, and each colour corresponds to a certain area of wavelengths:
| Colour | Wavelength / nm |
|---|---|
| purple | 400 - 450 |
| blue | 450 - 500 |
| green | 500 - 570 |
| yellow | 570 - 590 |
| orange | 590 - 620 |
| red | 620 - 760 |
X-rays → X-zrake
X-rays are electromagnetic radiation of shorter wavelength than ultraviolet radiation (10-11 m to 10-9 m or 0.01 nm to 1 nm) produced by bombardment of atoms by high-quantum-energy particles. X-rays can pass through many forms of matter and they are therefore used medically and industrially to examine the internal structure.
Citing this page:
Generalic, Eni. "Svjetlost." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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