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Physics > Quantum Theory And Matter > Flashcards

Quantum Theory And Matter Flashcards

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1
Q

Why was quantum theory developed?

A

Classical models where unable to explain experimental results like black body spectrum, atomic line spectrum and photoelectric effect.

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2
Q

What are line spectra?

A

It is when atoms absorb light at characteristic frequencies. It is a coloured band with black lines.

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3
Q

What is the emission spectra?

A

Atoms emit photons at specific frequencies. It is a black band with coloured stripes.

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4
Q

How did Bohr’s model differ from others?

A

It was able to explain the existence of atomic spectra and predict positions of the hydrogen spectra lines.

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5
Q

How are electrons in the Bohr model treated?

A

They are treated as standing waves.

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6
Q

What do the transitions of electrons between quantised energy levels correspond to?

A

The lines in the atomic spectra

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7
Q

What is each transition a result of?

A

A photon being absorbed or emitted.

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8
Q

What must a photon have when used in a transition?

A

The energy the corresponds exactly to the gap between energy levels.

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9
Q

What are the short falls of the Bohr model?

A

It cannot predict spectra of atoms other than hydrogen or explain line splitting.

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10
Q

Why are electrons known as having wave-particle duality?

A

Because they also have a wave nature.

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11
Q

Spectra are composed of two parts…

A

Continuous spectra and line spectra

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12
Q

Spikes of increased intensify around a single wavelength are…

A

Emission lines

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13
Q

Dips in the spectrum around a single wavelength are…

A

Absorption lines

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14
Q

When is an atom happiest with its electrons?

A

When they are in their ground state, ie with the lowest Englert they are allowed to have.

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15
Q

What happens when you supply energy to an electron?

A

It will jump to a higher level ie an excited state.

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16
Q

What happen if you put a lot of energy into an electron?

A

It will escape and the atom will become ionised.

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17
Q

What does it it mean when energy levels are quantised?

A

It means that electrons cannot be anywhere with any amount of energy. They must be at one of the levels and must have that levels corresponding charge.

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18
Q

What does only allowing certain energies for an electron mean?

A

It means an electron can only jump down by giving off a certain energy or jump up by absorbing that same certain energy.

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19
Q

What does the amount of energy a photon have depend on?

A

It’s frequency or wavelength, as they are related.

20
Q

How does an electron lose energy?

A

It must get rid of it in the form of light, the frequency of which is fixed by the amount of energy change.

21
Q

What happen is a photon of a specific energy required by an electron comes along?

A

The electron will absorb it a become excited.

22
Q

What gives patterns of line spectra?

A

As only certain energy gaps are allowed for each element, only certain wavelengths of light can be produced or absorbed.

23
Q

What is the most obvious reason for line broadening?

A

The Doppler effect

24
Q

What are the three methods of promoting an electron to a higher state?

A

Heat
Bombardment- other electrons that have a high potential to produce discharge.
Photon bombardment- irradiation with a specific frequency to achieve a specific transition

25
Q

When are characteristic x-Ray’s emitted?

A

When electrons in heavy elements make transition between the lower atomic energies.

26
Q

When is black body radiation emitted?

A

By all objects at non-zero temperatures

27
Q

What does a black body spectrum look like?

A

It is characteristic of the temperature of the body.

28
Q

What explains black body radiation?

A

The quantisation of electromagnetic energies

29
Q

What are photons?

A

Particles of electromagnetic energy

Packets of light

30
Q

What is the photoelectric effect?

A

It is the ejection of electrons from a polished metal surface by incident light. The light must have a minimum frequency for this to occur.

31
Q

What does the minimum energy correspond to.

A

The work function, W, of the metal

32
Q

What is cut off frequency?

A

The minimum frequency of light needed to eject an electron from a metal surface.

33
Q

What does quantised mean?

A

Existing in discrete amounts ie not able to be divided into arbitrarily small amount.

34
Q

What is a stopping voltage?

A

The reverse bias voltage required to stop the flow of photoelectric so in a photoelectric effect.

35
Q

What is the ionisation energy of a material?

A

It is the energy required to eject an electron from it, it’s work function.

36
Q

What is electron diffraction?

A

The interference of electrons due to the interaction of their probability waves.

37
Q

What is wave particle duality?

A

The dual nature of matter and energy, requiring both wave and particle models to completely explain all behaviour.

38
Q

Shorter wavelengths correspond with what kind of temperature?

A

High temperatures

39
Q

How to fluorescent light bulbs work?

A

The spectra of the gases inside them have sharp peak ie emit light in the visible spectrum.

40
Q

What metal will require the highest frequency light in order to emit photo electrons?

A

Which ever metal has the highest work function.

41
Q

How do electrons differ from photons?

A

Electrons have mass, photons do not
Photons always travel at c, electrons can have any v
Both act as a wave
Both produce intensity peaks at same position.

42
Q

What does deterministic mean?

A

Everything is inevitable and with enough info the future can be precisely predicted

43
Q

What does probabilistic mean?

A

There is a real element of chance, future cannot be precisely predicted.

44
Q

What is the significance of the negative sign at the ground state?

A

It means being bound to the nucleus to form an atom is a lower energy state than being free, ie energy in needed to remove the electron

45
Q

Shortest wavelength corresponds to…

A

Largest energy

Physics (7 decks)

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