A Level Physics Definintions

• de Broglie Wavelength


  The wavelength associated with a moving particle
• Electric Field

  Force per unit positive charge
• Mass Defect


  The difference between the total mass of the individual separate nucleons and the mass of the nucleus
• Decay Constant


  The probability that an individual nucleus will decay in a time interval
• Half Life


  The mean time taken for half of the active nuclei in a sample to decay
• Radiant Flux Density


  The radiant power passing normally through a surface per unit area.
• Activity

  The rate of decay of nuclei of a radioactive source

  
• Radioactive Decay

  The random and spontaneous process of
• Wein's Displacement Law


  The wavelength at maximum intensity is inverselyproportional to the thermodynamic temperature ofa black body
• Hubble's Law

  The recession speed of a galaxy is directly proportional to its distance from Earth.

  
• Redshift

  An increase in the observed wavelength of electromagnetic waves due to the recession of the source
• Specific Heat Capacity

  The energy needed to raise the temperature of 1kg of a substance by 1ºC
• Standard Candle

  An astronomical body of a known luminosity
• Luminosity


  The total radiant power emitted by a star
• Work Function Energy

  Minimum energy required to cause emission of an electronfrom the surface of a metal
• Photoelectric Effect


  Emission of electron when electromagnetic radiationis incident on the surface of a metal
• Electric Potential


  The work done per unit charge in bringing a point positive charge from infinity to a defined point

  
• Gravitational Field Strength


  The force per unit mass experienced by a test mass placed in the field.
• Binding energy

  The minimum energy needed to separate a nucleus into its constituent nucleons to infinity
• Ideal Gas


  A gas that obeys the relationship PV ∝ T where V is the volume of the gas and T is the thermodynamic temperature

  
• Photon


  A quantum of electromagnetic energy
• RMS value of current

  The steady current that delivers the same average power as the a.c. to a resistive load

  
• Lenz's Law


  The direction of induced EMF is such that it opposes the change causing it
• Faraday's Law


  The magnitude of the induced EMF is directly proportional to the rate of change of magnetic flux linkage
• Magnetic Flux Linkage

  The product of magnetic flux for a circuit and the number of turns
• Magnetic Flux

  The product of magnetic flux density and the cross-sectional area perpendicular to the direction of the magnetic flux density.
• Magnetic Flux Density

  The force acting per unit current per unit length on a wire placed at right angles to the magnetic field
• Magnetic Field


  A region where a current carrying conductor experiences a force
• Capacitance of a Parallel Plate Capacitor


  The ratio of the charge on one of the plates and the potential difference between the plates
• Gravitational Potential


  The work done per unit mass in bringing a test mass from infinity to a point in the field.
• Newton's Law of Gravitation


  The force between two point masses is directly proportional to the product of their masses and inversely proportional to the square of their separation

  
• Angular Speed


  The rate of change of angular displacement

  
• Radian

  The angle subtended at the center of a circle by an arc of length equal to the radius of the circle.
• de Broglie Wavelength


  The wavelength associated with a moving particle
• Electric Field

  Force per unit positive charge
• Mass Defect


  The difference between the total mass of the individual separate nucleons and the mass of the nucleus
• Decay Constant


  The probability that an individual nucleus will decay in a time interval
• Half Life


  The mean time taken for half of the active nuclei in a sample to decay
• Specific Acoustic Impedance
• Radiant Flux Density


  The radiant power passing normally through a surface per unit area.