Topic 3 2/2 Flashcards
Describe:
Atomic spectra
Range of frequencies of EM radiation emitted/absorbed by matter. 3 types of spectra:
Continuous, Line emission (Colour lines), Line absorption (Black lines)
Describe:
Incandescence
All matter vibrates, charges do so and release EM radiation. Increased temperature, increases oscillations of vibrations, thus frequency of EM, which can result in visible light being emitted.
Describe:
the changes in the spectrum of a filament globe as the temperature of the filament increases.
Increase in temperature will cause higher frequency EM radiation to be released, closer to violet colour.
Describe:
characteristics of the line emission spectra of elements.
When atoms of pure gas is heated or subject to potential difference. Light emitted is viewed through spectrometer/diffraction grating, showing color lines on dark.
Specific to each gas, thus can identify them.
Explain:
the uniqueness of the spectra of elements can be used to identify the presence of an element.
Emission spectra is specific to each atom as electron shells are different for each. Thus, a known gass’s emission spectra can be used to define its presence via discrete frequencies of light absorbed.
Explain:
production of characteristic X-rays in an X-ray tube.
Produced through incident electrons colliding and removing electrons in lower energy levels of target metals. Higher energy level electrons drop down to fill place, releasing X-ray photon with energy equal to the energy difference between the energy levels.
Describe:
Energy levels
There are different states in an atom, each with their own energy, which can be represented in energy-lvl diagram. Can be raised to excited states through having one electron not in ground state.
Explain:
magnitude of the transitions on an energy-level diagram relation to the region in the electromagnetic spectrum of the emitted photons
From higher to lower, photons are emitted with energy equal to the difference of energy levels the electron passed. Units of energy in eV
Describe:
Ionisation energy of an atom
the minimum energy required to remove a single electron from the atom in its ground state.
Describe:
line absorption spectrum of atomic hydrogen.
Only one electron with series dependant on ending level from 5 up.
Lyman series. N = 1 [UV]
Balmer series. N = 2 [Visible]
Paschen series. N = 3 [IR]
Explain:
why there are no absorption lines in the visible region for hydrogen at room temperature.
At room temperature, electron is in ground state, meaning that any transitions that occur will be in the Lymans series, requiring UV light, not visible.
Explain:
presence of absorption lines (Fraunhofer lines) in the Sun’s spectrum.
Sun produces white light, spanning the visible spectrum. Electrons in atoms of the suns atmosphere absorb photons with energy equal to the gap between lower/higher energy states. These incident photos are removed from the total light, resulting in the dark lines.
Describe:
Fluorescence
process of converting high-energy photons into a larger number of lower-energy photons
Describe:
Stimulated emission
a photon with energy corresponding to a transition from a higher-energy state to a lower-energy state is incident on an atom in the higher state, it can stimulate a transition to the lower state. This results in two identical photons
Compare
process of stimulated emission with that of ordinary (or spontaneous) emission.
Stimulated emission occurs when a photon of energy corresponding to a transition of high->low energy states is incident on an atom in the energy state, resulting in an incident photon and emitted photon which have equal energy.
Spontanious emission results in only one photon release, is also immediate.
Describe:
Conditions required for stimulated emission to predominate over absorption.
A population inversion is required. By having electrons in a metastable state, excited state with longer lifetime. Hence predominating over spontaneous emission.
Explain: function of laser
Within a laser, the grain medium absorbs energy, being excited to a metastable state usually. Eventual population inversion achieved and stimulated emission occurs. Mirrors continually reflect photons, one is partially reflective, allowing monochromatic, coherent, unidirectional light to pass.
Define:
Laser
Light Amplification by Stimulated Emission of Radiation.
Produces intense beam of coherent light
Describe”
Population inversion in a set of atoms
whenever there are more atoms in a higher-energy state than in a lower-energy state. For practical systems, the higher-energy state must be metastable if a population inversion is to be produced.
Describe:
useful properties of laser light
is coherent and monochromatic, unidirectional and may be of high intensity
Explain:
Safe handling of lasers
Protective eyewear that absorb laser light Protective gloves reduce burn Warning signs for active laser Electrical safety Fire extinguisher
Describe:
Standard model
Describes particles that form fundamental building blocks of matter and forces that govern their behaviour.
Fundamental particles are not made of smaller constituents
Quarks, leptons, gauge bosons
Describe:
gauge bosons
Photon - Electromagnetic
W, Z - Weak nuclear
Gluon - Strong Nuclear
Graviton - Gravitational
Describe:
Leptons and their properties
Lepton symbols
particles that are not affected by the strong nuclear force. Electron = e(-) = -1 Tau = t(-) = -1 Muon = U(-) = -1 And the neutrino equivalent: (Lepton)neutrino = V(lepton) = 0
Describe:
Quarks
fractionally charged particles that are affected by all of the fundamental forces, combine to form composite particles and are never directly observed or found in isolation.
Describe:
how protons, neutrons, and other baryons can be formed from different combinations of quarks.
Combinations of quarks for Hadrons which are bayrons or mesons.
Baryons are formed by 3 quarks that must be all quark or anti quark.
Describe:
Lepton numbers
Lepton numbers can be one of three types:
· electronic lepton number,
· muonic lepton number,
· tauonic lepton number,
The lepton number, regardless of type, for a lepton is 1. All other particles have a lepton number of 0.
Lepton neutrinos have their equivalent lepton number
Describe:
Baryon numbers
Quark number is ⅓, anti quark number is -⅓ . All other particles have a baryon number of 0
All baryons have number of +1
AntiBaryon has number -1
Describe:
Particle and antiparticle collision
they annihilate, releasing energy according to the mass–energy equivalence formula:
E=(delta)mc(squared)
Explain
Understanding of energy of photons released when electron transfer down through electron states
No energy higher than the ground state n=1
Energy = Upper state - Lower state
