Topic 3 2/2

Question 1

Describe:

Atomic spectra

Answer 1

Range of frequencies of EM radiation emitted/absorbed by matter. 3 types of spectra:
Continuous, Line emission (Colour lines), Line absorption (Black lines)

Question 2

Describe:

Incandescence

Answer 2

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.

Question 3

Describe:

the changes in the spectrum of a filament globe as the temperature of the filament increases.

Answer 3

Increase in temperature will cause higher frequency EM radiation to be released, closer to violet colour.

Question 4

Describe:

characteristics of the line emission spectra of elements.

Answer 4

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.

Question 5

Explain:

the uniqueness of the spectra of elements can be used to identify the presence of an element.

Answer 5

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.

Question 6

Explain:

production of characteristic X-rays in an X-ray tube.

Answer 6

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.

Question 7

Describe:

Energy levels

Answer 7

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.

Question 8

Explain:
magnitude of the transitions on an energy-level diagram relation to the region in the electromagnetic spectrum of the emitted photons

Answer 8

From higher to lower, photons are emitted with energy equal to the difference of energy levels the electron passed. Units of energy in eV

Question 9

Describe:

Ionisation energy of an atom

Answer 9

the minimum energy required to remove a single electron from the atom in its ground state.

Question 10

Describe:

line absorption spectrum of atomic hydrogen.

Answer 10

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]

Question 11

Explain:

why there are no absorption lines in the visible region for hydrogen at room temperature.

Answer 11

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.

Question 12

Explain:

presence of absorption lines (Fraunhofer lines) in the Sun’s spectrum.

Answer 12

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.

Question 13

Describe:

Fluorescence

Answer 13

process of converting high-energy photons into a larger number of lower-energy photons

Question 14

Describe:

Stimulated emission

Answer 14

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

Question 15

Compare

process of stimulated emission with that of ordinary (or spontaneous) emission.

Answer 15

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.

Question 16

Describe:

Conditions required for stimulated emission to predominate over absorption.

Answer 16

A population inversion is required. By having electrons in a metastable state, excited state with longer lifetime. Hence predominating over spontaneous emission.

Question 17

Explain:
function of laser

Answer 17

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.

Question 18

Define:

Laser

Answer 18

Light Amplification by Stimulated Emission of Radiation.

Produces intense beam of coherent light

Question 19

Describe”

Population inversion in a set of atoms

Answer 19

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.

Question 20

Describe:

useful properties of laser light

Answer 20

is coherent and monochromatic, unidirectional and may be of high intensity

Question 21

Explain:

Safe handling of lasers

Answer 21

Protective eyewear that absorb laser light
Protective gloves reduce burn
Warning signs for active laser 
Electrical safety
Fire extinguisher

Question 22

Describe:

Standard model

Answer 22

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

Question 23

Describe:

gauge bosons

Answer 23

Photon - Electromagnetic
W, Z - Weak nuclear
Gluon - Strong Nuclear
Graviton - Gravitational

Question 24

Describe:
Leptons and their properties
Lepton symbols

Answer 24

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

Question 25

Describe:

Quarks

Answer 25

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.

Question 26

Describe:

how protons, neutrons, and other baryons can be formed from different combinations of quarks.

Answer 26

Combinations of quarks for Hadrons which are bayrons or mesons.
Baryons are formed by 3 quarks that must be all quark or anti quark.

Question 27

Describe:

Lepton numbers

Answer 27

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

Question 28

Describe:

Baryon numbers

Answer 28

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

Question 29

Describe:

Particle and antiparticle collision

Answer 29

they annihilate, releasing energy according to the mass–energy equivalence formula:
E=(delta)mc(squared)

Question 30

Explain

Understanding of energy of photons released when electron transfer down through electron states

Answer 30

No energy higher than the ground state n=1

Energy = Upper state - Lower state