Quanta And Waves Flashcards
In Newtonian mechanics, when can the position and momentum of any particle be found?
When the starting details are known
Quantum mechanics says that it is only possible to calculate what?
Probabilities
What does the uncertainty principle say?
It is not possible to measure the position and the momentum of a particle with absolute certainty
What does the uncertainty principle in terms of energy and time lead to?
The concept of quantum tunnelling
What is an example of quantum tunnelling?
Alpha decay
Where are alpha particles emitted from?
Heavy nuclei
What are cosmic rays?
High energy charged particles originating in outer space
What percentage of particles are protons in cosmic rays?
89%
What does quantum mean?
The minimum amount of any physical property involved in an interaction
What does the quantum theory attempt to explain?
Phenomena and experimental observations which could not be explained by classical physics
What could classical physics not explain?
blackbody radiation, the photoelectric effect, spectra, atomic structure and electron diffraction.
What did Planck propose?
That energy existed in individual packets or quanta rather than as a constant electromagnetic wave
When does the photoelectric effect occur?
When electromagnetic radiation is directed at a metal surface and ejects electrons from the metal.
When charged particles from space approach the earth what are they affected by?
The Earth’s magnetic field
What happens when cosmic rays hit the top of the atmosphere?
They produce showers of secondary particles, including electrons, photons, neutrinos, and muons. These particles are called a cosmic air shower
Where do low energy cosmic rays come from?
The Sun
Where do intermediate energy cosmic rays come from?
The Milky Way
Where are the highest energy cosmic rays thought to have come from?
Galactic centres but their origin is still uncertain.
What is the term ‘particle’ used to describe?
Localised phenomena that transport mass and energy
What is the term ‘wave’ used to describe?
Spread out phenomena that carry energy but no mass
When electrons pass through a tiny opening or slit what do the produce?
Diffraction fringes
What is black body radiation?
The name given to the radiation emitted by hot objects
What is an ideal perfect radiator?
Black body
What is the term quantum used to describe?
A quantity which can only exist in discrete integer values
When is photoemission not possible?
Below the threshold frequency
What is the minimum energy required to cause photoemission called?
The work function
In the bohr model of the atom, what does the electron orbit circumfrence have to contain?
A whole number (n) of de broglie wavelengths
Does an electron gain or give off energy when it jumps to an outer orbit in an atom?
Gains
Does an electron gain or five off energy when it jumps from an outer orbit to an inner orbit in an atom?
Give off
What is the Bohr model able to explain?
Emmision line spectra and absorption line spectra
What properties does electromagnetic radiation have?
Particle properties and wave properties
What properties do electrons have?
Wave properties and particle properties
What are electrons and electromagnetic radiation said to exhibit?
Wave-particle duality
What properties does evidence of wave-particle duality come from?
Electrons behaving as particles, electron diffraction and interferance patterns
What properties suggest that electrons are particles?
They have a mass and can be accelerated
What can electromagnetic radiation produce?
Interferance patterns
What provides evidence that electromagnetic radiation has wave properties?
The fact they produce interferance patterns
What does Heisenberg’s uncertainty principle state?
It is impossible to determine accuratly both the position and the speed and direction of a quantum particle at the same time
In what plane does unpolarised light have oscillations perpendicular to its direction of travel?
Every plane
What is an example of polarisation?
A coating on sunglasses which cut down glare
When light is reflected from an electrical insulator such as glass or water
Where does interference by divisions of wave front take place?
Between two coherent waves which originated from the same wave front
When are waves said to be coherent?
If there is a constant phase difference between them
When does destructive interference occur?
If the phase difference between two overlapping coherent waves is π
When does the discharge occurs in the photoelectric effect?
Only when the light is above a certain threshold frequency, no matter how bright the light is
What happens when the frequency of the light increases but not with its intensity in the photoelectric effect?
The kinetic energy of the ejected electrons increases
In the photoelectric effect what does a more intense light do?
Releases more electrons.
How many planes will a polarising filter or polariser allow light to pass through
One plane only
How can we observe interference of light
A single source must be used which is passed through a single slit and then a double slit
How are the colours seen from reflected light, such as those from petrol on water, created?
By interference due to division of amplitude
What will a coherent source of waves produce?
Constructive interference if there is an optical path difference equivalent to a whole number of wavelengths, i.e. the waves will be in phase
Destructive interference if there is an optical path difference equivalent of an odd number, i.e. the waves will be completely out of phase
What is damping?
When the amplitude of oscillation decreases to 0
What path will a charges particle entering a uniform field at 90° to the field lines follow?
A circular path
What happens if a particle enters a magnetic field at angle θ?
Only a component of the particles velocity will be perpendicular to the magnetic field lines
What force is on the charged particle parallel to the magnetic field?
No force
What is the radius r of a circular orbit of a charged particle moving perpendicular to a magnetic field directly proportional to?
The mass and velocity of the charged particle
What is the radius r of a circular orbit of a charged particle moving perpendicular to a magnetic field inversely proportional to?
The magnetic induction and magnitude of the charge
What happens when charged particles collide with nitrogen?
A pink light is produced
What happens when charged particles collide with atomic oxygen?
A green light is produced
What is simple harmonic motion?
A type of oscillation where an object vibrates about an equilibrium position under the influence of an unbalanced force which always acts towards the equilibrium position. The magnitude of the unbalanced force is proportional to the object’s displacement, but in the opposite direction
Is there net mass transport in wave motion?
No
If the amplitude of a wave increases what happens to the energy?
It also increases
If the amplitude of a wave doubles , what happens to the intensity of the wave?
It increases 4 times
What is a node?
A position of 0 disturbance on a stationary wave
What are antinodes?
Points of maximum disturbance halfway between nodes
What causes a standing wave?
The superposition of the incident and the reflected wave
What is the definition for polarising?
An electric field vector oscillates in one plane
What is solar wind?
A stream of charged particles which escape from the upper atmosphere of the Sun. These are mostly electrons, protons and alpha particles
