Paper 1 Definitions Flashcards
Moment?
Force times perpendicular distance from pivot.
Couple?
A pair of of equal but opposite coplanar forces.
Threshold frequency?
Minimum frequency required to eject photoelectrons.
Work function?
Minimum energy required to remove an electron from the surface of a metal.
Photoelectric effect?
Emission of electrons from a metals surface when electromagnetic radiation is incident upon it.
Photoelectric emission?
Emission of electrons from a metal surface when light is directed at the surface.
Excitation?
An electron has gained enough energy to move to a higher energy level.
Ionisation?
When an electron gains enough energy to be completely removed from the atom from ground state.
Free fall?
Motion of an object when experiencing an acceleration of g.
Newton’s second law?
F = ma
Amplitude?
Maximum displacement from the equilibrium position.
Frequency?
Number of cycles per second passing a given point.
Wavelength?
Length of one whole wave cycle.
Phase?
Measurement of the position of a certain point along the wave cycle.
Phase difference?
Amount one wave lags behind the other.
Longitudinal wave?
Vibrations in same direction as energy transfer.
Transverse wave?
Vibrations perpendicular to the direction of energy transfer.
Elastic collisions?
KE conserved.
Impulse?
Change in momentum.
Stationary wave?
Superposition of two waves with the same frequency, moving in opposite directions.
Coherent sources?
Same wavelength and frequency, and a fixed phase difference between them.
Path difference?
Amount by which the path travelled by one wave is longer than the path travelled by the other wave.
Constructive interference?
Path difference is a whole number of wavelengths.
Destructive interference?
Path difference is half a wavelength or more half a wavelength value out of phase.
Monochromatic light?
Same frequency and wavelength.
Modal dispersion?
Light rays enter the fibre at different angles taking different paths, and so take different times to reach the end of the optical fibre.
Material dispersion?
Light consists of different wavelengths that travel at different speeds. This causes some light wavelengths to reach the end of the fibre faster.
1 joule?
Energy equal to the energy needed to raise a 1N weight through a height of 1 metre.
Electric current?
Rate of flow of charge.
Potential difference?
Work done per unit charge.
One coulomb?
Amount of charge that passes in 1 second if the current is 1 amp.
Ohmic conductor?
Current is directly proportional to the potential difference.
Thermistor?
A resistor with a resistance that depends on temperature.
Hooke’s law?
Extension is proportional to applied force.
Plastic deformation?
Material is permanently stretched.
Young modulus?
A measure of the stiffness of a material.
Power?
Rate of energy transfer.
Internal resistance?
When chemical energy in a battery causes electrons to move and collide with one another.
EMF?
Amount of electrical energy the battery produces for each coulomb of charge.
Proton number?
Total number of protons in the nucleus.
Nucleon number?
Total number of protons and neutrons.
Isotopes?
Atoms with the same number of protons but different number of neutrons.
Specific charge?
Charge to mass ratio.
Nuclear force?
The force that overcomes the electrostatic repulsion between protons in the nucleus to keep the protons and neutrons together.
Hypothesis?
An untested theory or idea.
Photon?
Pack of electromagnetic waves.
Scalar quantity?
Physical quantity which has magnitude only, no direction.
Vector quantity?
Physical quantity which has magnitude and direction.
Hadron?
Particles which feel the strong interaction.
Uniform circular motion?
When an object rotates at a steady or constant rate.
Centripetal force?
Resultant inward force towards the centre of the circle.
SHM?
Acceleration of an object is directly proportional to its displacement from its equilibrium position in the opposite direction, and is directed towards the equilibrium.
Free vibrations?
Involve no transfer of energy to or from the surrounding.
Forced vibrations?
When there is no external driving forces.
Natural frequency?
Frequency at which free oscillating systems oscillate at.
Resonance?
When an oscillating system is forced to vibrate at a frequency close to its natural frequency. The amplitude of vibration increases rapidly to a maximum.
