Flashcards
PH2 Definitions
Flashcards do conjunto (20)
- 1Progressive WaveA Pattern of disturbances travelling through a medium and carrying energy with it, involving the particles of the medium oscillating about their equilibrium positions.
- 2Polarised WaveA polarised wave is a transverse wave in which particle oscillations occur in only one of the directions at right angles to the direction of wave propergation
- 3Wavelength of a progressive waveThe wavelength of a progressive wave is the minimum distance measured along the direction of propagation between two points om the wave that are oscillating in phase
- 4Frequency of a waveThe frequency is the number of cycles of a wave that pass a point in one second.
- 5velocity of a waveThe distance that the wave profile moves per unit of time
- 6DiffractionThe spreading of waves when they meet obstacles. Some of the waves energy also travels into the geometric shadow of the wave.
- 7Principle of superpositionthis states that if two waves from two sources or travelling two different routes if from the same source occupy the same region then the total displacement at any one point will be the vector sum of their individual displacements
- 8In phaseWaves arriving at the same point are said to be in phase if they have the same frequency and are in the same point in their cycles at the same time.
- 9Phase differenceThis is the difference in position of 2 points within a cycle of oscillation. It is measured as a fraction of an cycle where one cycles is 360 degrees
- 10CoherenceWave or wave sources that have the a constant phase difference are coherent
- 11Stationary or standing waveA pattern of disturbances in a medium in which no energy is transferred.The amplitude of the oscillations is zero at nodes and maximum at anti-nodes.
- 12Snell's lawAt the boundary between two materials the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant
- 13Critical anglewhen light approaches the boundary between 2 media from the slower medium, the critical angle is the largest angle of incidence for which refraction can occur.
- 14Photoelectric effectiveWhen light or uv radiation of a high enough frequency electrons are emitted from the surface
- 15Work functionThe minimum energy required to remove an electron from a surface
- 16Stimulated emissionThis is the emission of a photon from an excited atom, triggered by an incident photon of energy equal to the energy gap between the excited state and a state of lower energy in the atom. The emitted photon has the same frequency, phase, direction of travel and polarisation direction as the incident photon.
- 17Population inversionA population inversion is a situation in which a higher energy state in an atomic system is more heavily populated than a lower energy state (i.e. a less excited state or the ground state) of the same system
- 18PumpingPumping is feeding energy into the amplifying medium of a laser to produce a population inversion
- 19Black BodyA black body is a body (or surface) which absorbs all the electromagnetic radiation that falls upon it. No body is a better emitter of radiation at any wavelength than a black body at the same temperature
- 20Luminosity of a starThe luminosity of a star is the total energy it emits per unit time in the form of electromagnetic radiation
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- FlashCards sobre PH2 Definitions, criado por rolo1197 em 05-06-2014.
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