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118 Cards in this Set
- Front
- Back
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Photoelectric Effect
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The emission of electrons from a metal as a result of light
with sufficiently short wavelength falling on it |
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Photon
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A quantum of electromagnetic energy
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Work function, Φ
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The work function of a material is defined as the minimum amount of energy required to remove a free electron from the surface of a material
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potential barrier
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A potential barrier is a region within which the potential energy of the particle is much higher than immediately outside it
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Ionisation Energy
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The ionization energy of an atom is the minimum energy required to remove an electron completely from the atom.
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Photoelectric effect
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a phenomenon that results in the liberation of electrons from a metal surface when electromagnetic radiation of high enough frequency falls on the metal.
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Stopping Potential
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The minimum value of the retarding potential difference required to stop the photoelectrons with maximum kinetic energy from reaching the collector.
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Threshold frequency
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The minimum frequency f0 required to cause photoemission from a metal of work function hf0.
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Binding Energy:
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The energy required to split a nucleus into its individual nucleons
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Nuclear Fission
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A nuclear process in which a heavy nucleus is split into lighter fragments of approximately equal mass, losing mass and releasing energy in the process.
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Nuclear Fusion
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A nuclear process in which two or more nuclides of low mass number are forced to fuse into a nuclide of higher mass number, losing total mass and releasing energy in the process.
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Radioactivity
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The spontaneous and random disintegration of an unstable nucleus into a more stable one by emitting alpha-particle, beta-particle and/ or gamma radiation
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Half-life
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The expected time taken for half the number of radioactive nuclei present (N) to decay, based on the average of a large number of radioactive nuclei for that particular radioactive isotope.
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Decay constant λ
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The probability that a single decay will occur within the unit of time specified.
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Spontaneous Emission
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A photon is emitted randomly and in any direction without any external stimulation
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Stimulated Emission
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An incoming photon, whose energy is exactly equal to the difference between two energy levels, induces the excited atom to fall into a lower energy level and releases a photon in the process.
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Population Inversion
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When there are more atoms in the excited state than in the ground state.
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Intrinsic Semiconductor
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A semiconductor without added impurities.
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Extrinsic semiconductor
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A semiconductor with added impurities.
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Energy Gap
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The energy difference between the base of the conduction band and the top of the valence band.
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P-N Junction
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A P-N junction is a single semiconductor crystal that has been selectively doped so that one region is n-type material and the adjacent region is p-type material.
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Stimulated Absorption
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When an atom at a lower energy level absorbs a photon and moves to a higher energy level.
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Magnetic Flux density
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The magnetic flux density B at a point is the force acting per unit current in a wire of unit length lying at right angles to the magnetic field and current.
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Tesla
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1 tesla is the magnetic flux density if a wire of length 1m carrying a current of 1A has a force of 1N exerted on it in a direction at right angles to both the magnetic flux and the current.
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Magnetic Flux:
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The magnetic flux is the product of the magnetic flux density normal to the plane of the surface and the area of that surface.
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Weber
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One weber is defined as the magnetic flux passing through an area of 1m2 placed in a magnetic field of flux density one tesla, with its surface perpendicular to the field.
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Magnetic Flux Linkage
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A coil of N turns of cross section A is placed in a magnetic field of flux density B with its axis along the field, has a flux linkage of Ф = N Ф = NBA
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Faraday’s Law
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The magnitude of the induced electromotive force is directly proportional to the rate of change of flux linkage.
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Lenz’s Law
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The direction of the induced e.m.f is such that the induced current will flow in the direction to produce an effect that would oppose the change that gives rise to the current.
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Coulomb’s Law of Electrostatic Force
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The electrostatic force F between two point charges Q1 and Q2 is directly proportional to the product of the charges and inversely proportional to the square of their distance r between them.
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Electric Field of Force
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A region of space in which a charge experiences a force due to electrical effect of another charge.
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Electric field strength
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The electric field strength E at a point P in an electric field is defined as the electric force per unit charge on a positive test charge placed at that point P.
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Potential Energy, U
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The electric potential, U of a charge q at a point in an electric field is defined as the work done by an external agent to move a charge q from infinity to that point at infinitesimally small speed.
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Electric Potential, V
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The electric potential V at a point in an electric field is defined as the work done per unit positive charge by an external agent to move a charge from infinity to that point at infinitesimally small speed.
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Gravitational potential energy
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The gravitational potential energy of a mass, m, placed at a point in the gravitational field is defined as the work done in bringing it from infinity to that point.
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Gravitational potential, Φ
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The gravitational potential, Φ, at a point in a gravitational field is defined as the work done per unit mass in bringing a test mass from infinity to that point.
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Gravitational field strength, g
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The gravitational field strength, g, at a point in a gravitational field is defined as the gravitational force per unit mass acting on a body placed at that point.
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Gravitational field
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The gravitational field is a region where a gravitational force is experienced by another mass placed in it.
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Newton’s Law of Gravitation
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Every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them.
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Diffraction
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Diffraction is the spreading of waves when they pass through an opening or around an obstacle.
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Coherence
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Two waves are coherent when the phase difference between them is constant.
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Path Difference
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the difference between the distances travelled by two waves.
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Interference
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Interference is the phenomenon where two or more waves of the same type superpose to give a resultant wave.
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Principle of Superposition
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If two or more waves of the same kind exist simultaneously at a point, the resultant displacement is the vector sum of the individual displacements due to the waves at this point.
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Root Mean Square
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The root-mean-square of an alternating current (or voltage) is defined as that value of steady direct current (or voltage) which would dissipate energy at the same rate in a given resistance.
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Electromotive force
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E.m.f is defined as the energy converted from other forms into electrical energy by a source in driving a unit charge round a complete circuit.
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Ohm’s Law
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The current through an ohmic material is directly proportional to the potential difference across it, provided there is no change in the physical conditions of the conductor.
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Ohm
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The ohm is defined as the resistance of a conductor through which a current of 1A flows when then potential difference across it is 1 volt.
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Volt
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1 volt is the potential difference between two points in a circuit in which 1 joule of energy is converted to other forms when 1 coulomb of charge passes between them.
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Potential Difference
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Potential difference between two points in a circuit is defined as the amount of electrical energy converted into other forms of energy per unit of charge flowing between them.
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Coulomb
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quantity of electric charge that passing a given point when a current of one ampere flows for one second
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Charge
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The product of current and time.
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Electric Current
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The rate of flow of positive charge.
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First Law of Thermodynamics
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The increase in the internal energy of the system is equal to the sum of the heat supplied to the system and the work done on the system.
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Ideal gas
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A gas which obeys the ideal gas equation pV = nRT at all values of Pressure, Volume and Temperature.
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Specific latent heat
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The specific latent heat (L) of fusion (or vaporization or sublimation) of a substance is the thermal energy required per unit mass of the substance to change from solid to liquid (or liquid to vapour, or solid to vapour) at constant temperature.
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Latent Heat
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Latent heat is the heat energy which a body will absorb during melting, evaporation or sublimation and which is gives out during freezing or condensation.
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Specific Heat Capacity, c
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c, of a substance is the amount of heat energy needed to raise the temperature per unit mass of the substance by one degree.
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Thermal Equilibrium
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Two bodies in thermal contact are said to be in thermal equilibrium when there is no net heat flow between them. Net heat flow is determined by the temperatures of the bodies in the question. Two bodies in thermal equilibrium with each other have the same temperature.
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Critical Damping
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Critical damping is where the system, when displaced and released, returns to equilibrium, withing one complete oscillation.
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Forced oscillation
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An resulting oscillation when a periodic driving force is applied to a system.
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Resonance
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Resonance is when energy is added to an oscillating system without any leakage.
This occurs when a system, having a natural frequency f0, is acted upon by a periodic driving force of the same frequency. |
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Damping
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The process whereby dissipative forces act to remove energy from an oscillating system, causing the amplitude of oscillation to decrease with time.
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Simple Harmonic Motion
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SHM: An oscillatory motion in which the object’s acceleration directly is proportional to its displacement AND its acceleration is always oppositely directed to its displacement.
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Polarization
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The process by which the oscillations of a wave are made to occur in one direction only.
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Stationary waves
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Waves that effectively do not progress. They are the result of the superposition of two waves of similar amplitude, frequency and plane travelling in opposite directions.
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Intensity
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The intensity of a wave motion at a point is defined as the power per unit area incident normally to the surface at that point.
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Phase difference
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The fraction of one cycle by which one wave moves behind the other.
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Frequency, f
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The number of cycles which a particle undergoes per unit time.
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Period, T
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The time taken for an individual particle to undergo a complete oscillation. It is also the time taken for the wave to travel one wavelength.
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Wavelength
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The wavelength of a progressive wave is the distance between two adjacent points which are in phase. In particular, it is the separation of two adjacent crests or troughs.
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**The wavelength of a standing wave
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The wavelength of a standing wave is twice the distance between two nodes or between two antinodes
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Amplitude, A
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The maximum displacement of a particle from its equilibrium position.
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Displacement of a particle in a wave motion, x
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The displacement (x) of a particle in a wave motion is the distance between its current position and its equilibrium position.
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Longitudinal Waves
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A wave which has particles oscillating in a direction parallel to the propogation of the wave.
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Transverse Waves
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A wave which has particles oscillating in a direction perpendicular to the propogation of the wave.
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Linear Velocity
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The tangential velocity of a particle moving in a circular path.
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Uniform Circular Motion
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Refers to an object travelling at a constant speed on a circular path.
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Angular Velocity
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The rate of change of angular displacement per unit time.
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Radian
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One radian is the angle subtended at the center of a circle by an arc that is equal in length to the radius of the circle.
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Angular displacement
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The angle in radians through which a point of line has been rotated in a specific sense about an axis.
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Watt
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One watt is defined as the power when the amount of work done is 1 joule per second.
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Power
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The rate at which work is done. OR The rate at which energy is converted.
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Potential Energy
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The energy which a body possesses due to its position or to the arrangement of its component parts.
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Kinetic Energy
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The energy which a body possesses solely due to its state of motion.
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Principle of Conservation of Energy
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The total energy in an isolated system is always constant. Energy cannot be created or destroyed but can be converted from one form to another.
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Energy
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The ability to do work.
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Joule
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1 joule is the work done when a force of 1 newton moves a distance of 1 metre in the direction of the force.
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Work done by a force
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The product of force and the distance moved in the direction of the force.
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Principle of conservation of momentum
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The total momentum of an isolated system remains constant.
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Impulse
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Defined as a force multiplied by the amount of time it acts over.
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Weightlessness
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The absence of the sensation of contact forces.
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Apparent weight
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The measure of the normal contact force between a person and the surface he is in contact with.
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Weight
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The force exerted on a body due to gravity.
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Mass
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The measure of a body’s inertia.
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Force
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Rate of change of momentum.
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Linear Momentum
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The linear momentum of a body is the product of its mass and its velocity.
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Newton’s Third Law of Motion
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For every action, there is an equal and opposite reaction due to the interaction between the two bodies.
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Newton’s Second Law of Motion
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The rate of change of momentum of a body is proportional to its net force that acts on it and the momentum change takes place in the direction of the force.
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Newton’s First Law of Motion (Law of Inertia)
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A body at rest remains at rest, and a body in motion in a straight line remains in that state of motion unless acted on by a net force.
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Rigid body equilibrium
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For a body to be in rigid body equilibrium the resultant force acting on the body is zero and the resultant moment about any point acting on the body is zero.
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Couple
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Two equal and opposite forces whose lines of action do not coincide form a couple.
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Principle of Moments
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For a body to be in equilibrium, the sum of clockwise moments about the pivot must be equal to the sum of anti-clockwise moment about the pivot.
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Moment of a force
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The product of the force and the perpendicular distance from the pivot to the line of action of the force.
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Centre of Gravity
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The point through which the whole weight of an object appears to act.
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Friction
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A contact force that opposes motion.
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Principle of Flotation
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A body floating in a liquid always displaces its own weight of liquid.
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Archimedes’ Principle
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The upthrust acting on an object is equal to the weight of fluid displaced.
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Pressure
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Pressure is defined as the perpendicular force acting per unit area of a surface.
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Hooke’s Law
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Within its limit of proportionality, the applied force, F, on a spring is directly proportional to its extension, x.
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Acceleration
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The rate of change of velocity
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Velocity
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The rate of change of displacement
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Speed
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The rate of change of distance
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Displacement
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The straight line distance moved in a specified direction
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Accuracy
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An accurate set of measurements is one where the mean value is very close to the true value
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Precision
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A precise set of measurements is one where the readings have a very small scatter about the true value.
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Systematic Errors
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An error that causes the results to be always higher or always lower than the true value
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Random Errors
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An error that causes irregularities in the experiment, resulting in readings that are scattered about the true value.
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