Madrid PAU Physics flashcards
Madrid PAU Physics · Build recall with a focused review session.
30 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Refractive index
- The ratio of the speed of light in a vacuum to the speed of light in a medium, For light incident from vacuum or approximately air, it also equals sin(incidence)/sin(refraction); for two general media that ratio is their relative refractive index.
- Critical angle
- The angle of incidence in the denser medium for which the angle of refraction in the less dense medium is exactly ninety degrees. Beyond it total internal reflection occurs.
- Total internal reflection
- The complete reflection of light back into a denser medium when it strikes the boundary at an angle of incidence greater than the critical angle. It is used in optical fibres.
- Diffraction
- The spreading of waves as they pass through an aperture or around an obstacle, becoming more pronounced when the wavelength is comparable to the gap or obstacle size.
- Interference
- The superposition of two or more waves to produce regions of reinforced and cancelled displacement. Constructive interference gives maxima; destructive interference gives minima.
- Coherent sources
- Two wave sources that maintain a constant phase difference and have the same frequency, so that a stable interference pattern can be observed. Lasers provide a common example.
- Standing wave
- A wave pattern formed when two waves of equal frequency and amplitude travel in opposite directions, producing fixed nodes and antinodes. Energy is not transported along the medium.
- Resonance
- The large-amplitude oscillation that occurs when a system is driven at a frequency matching one of its natural frequencies. It is used in tuning circuits and musical instruments.
- Capacitance
- The charge stored per unit potential difference across a capacitor, measured in farads. For a parallel-plate capacitor it equals permittivity times area divided by plate separation.
- Time constant
- For a capacitor-resistor circuit, the product of resistance and capacitance; it is the time for the charge to fall to about thirty-seven per cent of its initial value during discharge.
- Electric field strength
- The force per unit positive charge experienced at a point in an electric field, measured in newtons per coulomb. It is a vector quantity with direction along the field line.
- Potential difference
- The energy transferred per unit charge when charge moves between two points in a circuit, measured in volts. It is the work done per coulomb.
- Electromotive force
- The energy supplied by a source per unit charge driven around a complete circuit, measured in volts. It differs from terminal potential difference when internal resistance is present.
- Internal resistance
- The resistance within a source of electromotive force that causes the terminal potential difference to fall as the current drawn increases. It dissipates energy as heat inside the source.
- Electromagnetic induction
- The generation of an electromotive force in a conductor when the magnetic flux linking it changes. The induced emf is proportional to the rate of change of flux linkage.
- Magnetic flux
- The product of the magnetic flux density and the area perpendicular to it, measured in webers. Flux linkage multiplies this by the number of turns in a coil.
- Lenz's law
- The direction of an induced current is such that it opposes the change producing it. This is a consequence of conservation of energy and gives the negative sign in Faraday's law.
- Work function
- The minimum energy needed to remove an electron from the surface of a metal. It is a property of the metal and appears in the photoelectric equation.
- Photoelectric effect
- The emission of electrons from a metal surface when light of frequency above a threshold falls on it. It demonstrates the particle nature of light.
- Threshold frequency
- The lowest frequency of incident radiation that can just cause photoelectric emission from a given metal surface. Below it, the ordinary weak-illumination single-photon model predicts no emitted photoelectrons.
- Half-life
- The time taken for half the nuclei in a given radioactive sample to decay, or for the activity to fall to half its initial value. It is constant for a given isotope.
- Decay constant
- The probability per unit time that an individual nucleus will decay. It is related to half-life by the expression lambda equals natural log of two divided by half-life.
- Activity
- The number of nuclear disintegrations occurring per second in a radioactive sample, measured in becquerels. It decreases exponentially with time according to the decay constant.
- Mass defect
- The difference between the total mass of the separate nucleons in a nucleus and the mass of the assembled nucleus. It appears as binding energy according to mass-energy equivalence.
- Binding energy
- The energy required to separate a nucleus completely into its individual protons and neutrons. It equals the mass defect multiplied by the square of the speed of light.
- Systematic error
- A consistent deviation of measurements from the true value in one direction, caused by faulty apparatus or flawed method. It affects accuracy but not necessarily precision.
- Random error
- Unpredictable variation in measurements about a mean value, caused by fluctuating conditions or limited resolution. It reduces precision and can be lessened by averaging repeated readings.
- Accuracy
- How close a measured value is to the accepted true value. It is affected mainly by systematic error, whereas precision concerns the spread of repeated readings.
- Precision
- The degree of agreement among repeated measurements of the same quantity, reflected in a small spread of values. It is affected by random error and instrument resolution.
- Restoring force
- A force directed toward equilibrium, often proportional to displacement over an explicitly specified linear range; its direction determines the sign in the oscillator equation.