Quanta & Waves Flashcards
Definitions from AH unit 2
What is meant by the “Ultraviolet catastrophe”?
Classical Physics models of peak wavelength vs frequency showed that the as the frequency increased the model tended to infinite energy being emitted.
What is the “Plum pudding” model of the atom?
That the atom was made up of negatively charged particles spread throughout a positively charged region, like plums in a plum pudding.
What is the “Rutherford” model of the atom?
That the atom is mostly empty space, with a dense positively charged core known as the nucleus of the atom.
What is the “Bohr” model of the atom?
That the atom has a dense positively charged core known as the nucleus of the atom, with electrons occupying discrete energy levels or “shells”.
What is meant by the “De Broglie wavelength” of a particle?
That all particles exhibit wave-like properties, with the wavelength inversely proportional to the momentum of the ‘particle’.
What are the implications of the “Uncertainty principle” for experimental measurements of position and momentum?
The precise position of a particle/system and its momentum cannot both be known simultaneously.
What are the implications of the “Uncertainty principle” for experimental measurements of energy and lifetime?
The precise energy and lifetime of a particle cannot both be known simultaneously.
What is meant by “Quantum tunnelling”?
A quantum particle can exist in a position that, according to classical physics, it has sufficient energy to occupy.
What is meant by “Cosmic rays”?
A stream of high energy particles and some rays, originating outwith our Solar System.
What is the most common component of “Cosmic rays”?
Protons
What is meant by an “Air shower”?
The large chain of reactions caused when a cosmic ray is incident on a atom or molecule in the upper atomsphere.
How are Cosmic rays detected through “direct” detection?
Above the atmosphere, by high altitude balloons or satellites.
How are Cosmic rays detected through “indirect” detection?
At ground level, by detecting the resulting air shower particles that reach the Earth’s surface.
What is meant by a “Sunspot”?
A region on the surface of the Sun which is cooler than that of the surrounding area, due to the magnetic field of a prominence preventing the hot gas rising to the surface.
What is meant by the “Solar wind”?
Stream of high energy charged particles from the Sun.
What is meant by “Simple harmonic motion”?
When an object is displaced from its equilibrium or rest position, and the unbalanced Force is proportional to the Displacement of the object and acts in the opposite direction, the motion is said to be Simple Harmonic.
What is meant by an “Under-damped” oscillating system?
A system in which the object will oscillate back and forth around an equilibrium point, losing energy each cycle until it comes to rest at equilibrium.
What is meant by a “Critically-damped” oscillating system?
A system where the frictional force which is just enough to bring the oscillating object to rest at equilibrium quickly, without passing the equilibrium point.
What is meant by a “Over-damped” oscillating system?
A system with a large resistance to motion, taking a long time to reach the equilibrium position (if at all).
What is meant by a “Wave”?
A transfer energy from one point to another with no net transfer of mass.
What is meant by the “Intensity” of a wave?
The energy that passes though unit area perpendicular to the wave direction in a time of one second.
How is the Intensity or energy of a wave related to its amplitude?
The intensity I (or energy E) of a wave is proportional to the square of its amplitude.
What phase change will occur on reflection if moving to a higher optical density?
phase change of π
What phase change will occur on reflection if moving to a lower optical density?
no phase change
What are the conditions for “Constructive interference”?
Coherent waves meeting “In Phase”
What are the conditions for “Destructive interference”?
Coherent waves meeting “Out of Phase”
How is a stationary wave formed?
Stationary waves are formed when transmitted and reflected waves interfere with each other.
What is meant by “Geometric path difference”?
The physical difference in the lengths of the paths traveled by two waves.
What is meant by “Optical path difference”?
The physical difference in the lengths of the paths traveled by two waves, multiplied by the refractive index of the material to take refractive changes into account.
What is meant by the “Division of Amplitude”?
Division of the energy of a wave being partially transmitted and partially reflected when incident on a surface between two media of different refractive index.
What is meant by a “bloomed” lens?
A lens to which a non-reflective coating has been applied.
What is meant by “Division of Wavefront”?
Division of a wave by splitting a single wavefront into two or more parts, through the use of a slit or other gap.
What is meant by “Unpolarised light”?
Light that consists of electromagnetic waves whose electric fields oscillate in more than one plane.
What is meant by “Polarised light”?
Light that consists of electromagnetic waves whose electric fields oscillate in only one plane.
What is meant by “Brewster’s angle”?
The angle of incidence at which the reflected and refracted rays are 90 degress apart. At this angle, the reflected ray will be fully polarised.
