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**2.**a quantum of light**3.**volt the energy an electron requires as it rises through a potential difference of one volt**4.**the distance any point on the wave has moved from its rest position**6.**the maximum displacement**7.**the spreading out of waves as they pass through a gap or around an obstacle**8.**velocity the average velocity of an electron as it travels through a wire due to potential difference**11.**the smallest distance between points that have the same pattern of oscillation**17.**duality the theory that states all objects can exhibit both wave and particle properties**19.**wave transfer of energy without transfer of matter**21.**the change in speed of a wave due to the change in density**23.**one joule per coulomb**24.**the total charge supplied by a current of 1amp flowing for 1 second**27.**wave a wave in which the vibrations are parallel to the direction of wave travel**28.**polarised wave a transverse wave oscillating in only one plane**29.**point on a stationary wave at which there is no displacement of the particles at any time**30.**difference the distance by which one wave lags behind another measured in wavelengths**31.**the energy transferred by a 1kW device in 1 hour**33.**function the minimum energy required to release an electron from a metal**36.**difference the electrical energy transferred per unit charge when electrical energy is converted into another form of energy**37.**two waves with a constant phase relationship**38.**the number of complete oscillations per unit time at any point**39.**difference the difference by which one wave lags behind another, measured in radians

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**1.**point on a stationary wave where the displacement of the particles varies by the maximum amount**5.**when two or more waves are in the same place at the same time they add together resulting in a new wave**9.**law the current through a conductor is proportional to the potential difference across it provided the physical conditions remain constant**10.**the process of turning unpolarised waves into a plane polarised wave**12.**wave a progressive wave possessing both electrical and magnetic field vibrations at right angles**13.**frequency the lowest frequency of electromagnetic radiation that will result in the emission of photoelectrons from a specified metal surface**14.**energy transferred per unit time**15.**when two or more waves of the same type exist in the same place at the same time, the resultant wave is found by adding the displacements of each individual wave**16.**second law the sum of the emf's is equal to the sum of the pd's in a closed loop**18.**potential difference divided by current**19.**effect the emission of electrons from the surface of a metal when electromagnetic radiation in incident on the surface**20.**the ratio of the product of resistance and cross-sectional area of a component and its length**22.**force the energy transferred per unit charge when one type of energy is converted into electrical energy**25.**power divided by area**26.**first law the sum of the currents entering any junction is equal to the sum of the currents leaving the junction**32.**wave a wave in which the vibrations are perpendicular to the direction of wave travel**33.**one joule per second**34.**resistance the resistance of a battery or a cell**35.**law I=Iocos2θ**36.**the time taken for one complete pattern of oscillation to take place at any point