Click on the read more to get a glossary of the terms for this unit. I will try to update it as I think of more words that I need to add, or try the quizlet for revision
https://quizlet.com/203360201/flashcards
| Term | Definition |
|---|---|
| absolute refractive index | the absolute refractive index (or just the refractive index), n , of a medium is the ratio of the speed of light in a vacuum to the speed of light in the material. (also the ratio of the wavelength of light in a vacuum to the wavelength of light in the medium) |
| angle of incidence | the angle between the incident ray and the normal. |
| angle of refraction | the angle between the refracted ray and the normal. |
| atomic mass units (u) | by definition one twelfth of the mass of a carbon-12 nucleus. |
| atomic number | the number of protons in an atomic nucleus. It is this number that determines the element and its properties. |
| binding energy | the energy needed to split a nucleus into its separate nucleons (not on the CfE Higher course) |
| chain reaction | when a nucleus undergoes fission it releases neutrons that can go on to cause further fission reactions by interactions with other nuclei. If there is a sufficient concentration of suitable nuclei, the process becomes self-sustaining. |
| coherent waves | coherent waves are waves that have the same frequency, speed and have a constant phase relationship. |
| collimator | part of a spectrometer that is used to produce a parallel beam of light. |
| constructive interference | when waves arrive at a point in phase or crest meets a crest and trough meets a trough resulting in a wave of larger amplitude than the individual waves. |
| critical angle | the angle above which total internal reflections occurs. Or, the maximum value of the angle between the normal and the ray in glass, θ glass, for which refraction can occur. |
| destructive interference | when waves arrive at a point in out of phase or crest meets a trough resulting in a wave of smaller amplitudeas the waves cancel out. |
| diffraction | an effect that causes waves to bend as they go past the end of an obstacle or through a small gap in a barrier. |
| dispersion | the process of splitting up light into its constituent colours, this can be done with a prism and white light. |
| electromagnetic waves | the spectrum of waves that includes radio, visible light, X-rays etc which all have no mass and travel at the speed of light in a vacuum. |
| excited state | any atomic energy level higher than the ground state. |
| ferromagnetic | materials in which the magnetic fields of the atoms line up parallel to each other in regions known as magnetic domains. |
| fission | the splitting of a large atomic nucleus into smaller fragments, with the resultant release of excess energy. |
| gold leaf electroscope | device used to measure small amounts of charge. |
| grating | a transparent slide of glass or plastic that has a very large number of equally spaced grooves machined on to its surface. Each groove acts as a source for coherent beams of light. |
| ground state | the lowest energy level of an atom where an electron has the lowest energy level. |
| induced fission | the deliberate splitting of a large nucleus caused by the collision of the nucleus with a neutron. |
| interference | a phenomenon in which two waves superpose to form a resultant wave of greater, lower, or the same amplitude. |
| ionisation level | the energy level at which an electron can break free from an atom. |
| irradiance | the power per unit area of radiation incident on a surface. |
| isotopes | different forms of the same element. The isotopes of an element contain the same number of protons but have different numbers of neutrons. (Many isotopes are unstable and can emit nuclear radiation) |
| line absorption spectrum | a spectrum that consists of narrow dark lines across an otherwise continuous spectrum. |
| line emission spectrum | a spectrum consisting of narrow lines of light, the position of which depend on the substances producing the light. |
| magnetic domains | regions in a ferromagnetic material where the atoms are aligned with their magnetic fields parallel to each other. |
| magnetic field | a magnetic field is a region in which a moving charge experiences a magnetic force. |
| magnetic poles | one way of describing the magnetic effect, especially with permanent magnets. There are two types of magnetic poles - north and south. Opposite poles attract, like poles repel. |
| mass defect (do not confuse with mass difference) | the difference between the mass of a nucleus and the total mass of an equal number of individual nucleons. |
| mass difference | the difference in mass between the reactants and products in a nuclear reaction. The resulting mass difference is converted to energy according to the equation E=mc 2 . |
| mass number | the total number of nucleons (protons and neutrons) in the nucleus of an atom. |
| monochromatic | radiation consisting of a single frequency. |
| monochromatic light | light of one wavelength (and therefore one colour) |
| normal | a line drawn at right angles to a surface or the boundary between two different media |
| nucleon | the general term for protons and neutrons (contained in the nucleus). |
| nuclide | the nuclei of one particular isotope. These nuclei all have the same atomic number and mass number. |
| path difference | the difference in path lengths of two sets of waves. |
| phase | denotes the particular point in the cycle of a waveform. |
| photocathode | the terminal from which electrons will be emitted due to the photoelectric effect. |
| photoelectric effect | the emission of electrons from a metal due to the effect of electromagnetic radiation. |
| photoelectrons | free electrons produced by the photoelectric effect |
| photoemission | the emission of electrons from a material caused by light shining on it. |
| photon | the particle of electromagnetic radiation. |
| potential difference | the potential difference between two points is a measure of the work done in moving one coulomb of charge between the two points. |
| principle of reversibility | the principle of reversibility states that a ray of light will follow the same path in the opposite direction when it is reversed. |
| prism | a prism is a transparent optical element with flat, polished surfaces that refract light. A dispersive prism can be used to break light up into its constituent spectral colours. |
| quanta | a "packet" certain amount, often referring to the energy of photons. |
| radioactive decay series | a chain of radioactive decays as a radioactive element changes to eventually become a stable, non-radioactive element. |
| radioisotope | short for radioactive isotope. |
| radionuclide | short for radioactive nuclide. |
| refraction | refraction occurs when a wave goes from one medium into another. When a wave is refracted, its speed and wavelength change; its frequency remains constant; its direction sometimes changes. |
| spectrometer | an instrument that can make precise measurements of the spectra produced by different light sources. |
| spontaneous fission | the random splitting of a large atomic nucleus due to the internal processes within the nucleus. (it does not require neutrons to cause the reaction and so is not of use in a nuclear reactor). |
| stopping potential | the minimum voltage required to reduce photoelectric current to zero. |
| telescope | the part of a spectrometer through which the spectrum is viewed. |
| threshold frequency | the minimum frequency of electromagnetic radiation that will cause photoemission for a particular substance. |
| total internal reflection | when a ray of light travelling in a more dense substance meets a boundary with a less dense substance at an angle greater than the critical angle, the ray is not refracted but is all reflected inside the more dense substance. |
| turntable | the stage or platform of a spectrometer on which the grating or prism sits. The turntable has an angular scale on it to allow measurements to be made. |
| work function | the minimum energy required to cause photoemission from a substance. |
