Excitation occurs when an electron absorbs a photon and gains enough energy to move up to a higher energy level.

Define de-excitation .

De-excitation occurs when an electron emits a photon and moves down to a lower energy level.

Ionisation occurs when an atom gains or loses an orbital electron and becomes charged.

What is the ionisation energy of an atom?

The minimum energy required to remove an electron from the ground state of an atom.

In a fluorescent tube, beam electrons .......... with electrons in mercury atoms, transferring kinetic energy.

In a fluorescent tube, beam electrons collide with electrons in mercury atoms, transferring kinetic energy.

What happens to the UV photons emitted by mercury atoms in a fluorescent tube?

They collide with electrons in the phosphor coating , exciting them; these phosphor electrons then de-excite, emitting photons in the visible light range.

True or False? An electron can only be removed from the ground state of an atom during ionisation.

False. An electron can be removed from any energy level it occupies; the ionisation energy specifically refers to the minimum energy needed to remove an electron from the ground state .

Define ground state .

The ground state is the lowest energy level that an electron in an atom can occupy, corresponding to the most negative energy.

Define line spectrum .

A line spectrum is a series of discrete lines, at specific wavelengths, produced when excited atoms emit or absorb light; each element produces a unique line spectrum.

How does an emission spectrum appear?

A series of discrete coloured lines on a black background, each corresponding to a wavelength emitted when an electron transitions from a higher to a lower energy level.

How does an absorption spectrum appear, and how is it produced?

A continuous spectrum with dark lines at certain wavelengths, produced when white light passes through a cool, low-pressure gas ; the missing wavelengths match the wavelengths present in the element's emission spectrum.

The energy of a photon emitted during an electron transition is equal to the .......... in energy between the two energy levels involved.

The energy of a photon emitted during an electron transition is equal to the difference in energy between the two energy levels involved.

True or False? Every element produces the same line spectrum, since all atoms contain electrons occupying energy levels.

False. Each element produces a unique set of spectral lines, so elements can be identified from their line spectrum.

Define wave-particle duality .

Wave-particle duality is the phenomenon whereby light (and matter) can behave as both a particle and a wave, depending on the situation.

What evidence supports light behaving as a wave ?

The diffraction and interference of light, for example in Young's double-slit experiment.

What effect does increasing the intensity of light, above the threshold frequency, have on photoelectron emission?

More photoelectrons are emitted per second; the kinetic energy of the individual photoelectrons is unaffected.

A larger accelerating voltage .......... the diameter of the electron diffraction rings.

A larger accelerating voltage reduces the diameter of the electron diffraction rings.

True or False? Wave theory correctly predicts that the kinetic energy of photoelectrons increases with the intensity of incident light.

False. Wave theory predicts this, but it is not observed ; increasing intensity above the threshold frequency increases the number of photoelectrons emitted, not their kinetic energy — this is why wave theory fails to explain the photoelectric effect.

How does increasing the momentum of a particle affect its de Broglie wavelength?

The de Broglie wavelength decreases — the greater the momentum, the smaller the wavelength.

In electron diffraction, what effect does increasing the speed (and momentum) of electrons have on the diffraction angle?

The angle of diffraction decreases .

Define electron diffraction .

Electron diffraction occurs when electrons passing through a slit similar in size to their de Broglie wavelength spread out, exhibiting wave-like behaviour.

What can the diffraction pattern of electrons passing through a crystalline solid be used to determine?

The structure of the crystal (arrangement of atoms) producing the pattern.

Why are high-energy electrons used to investigate the size of the atomic nucleus?

High-energy electrons have a shorter de Broglie wavelength , allowing much smaller structures, such as the nucleus, to be resolved.

Increasing the accelerating voltage increases the kinetic energy of electrons, which .......... their de Broglie wavelength.

Increasing the accelerating voltage increases the kinetic energy of electrons, which decreases their de Broglie wavelength.

How does increasing the kinetic energy of electrons affect the spacing of the diffraction rings observed?

The rings appear closer together , because the wavelength decreases as kinetic energy (and momentum) increase.

How is the radius of an electron diffraction pattern related to wavelength?

A longer wavelength produces a larger radius; a shorter wavelength produces a smaller radius.

True or False? Electrons with a smaller momentum produce a sharper, more tightly-defined diffraction pattern.

False. Electrons with smaller momentum have a longer de Broglie wavelength, which produces a larger radius and a more diffuse diffraction pattern, not a sharper one.

Peer review is the process by which scientific claims published in journals are evaluated by other experts in the field before being accepted.

Name the three things scientists check for during peer review.

Validity – is the method appropriate and are any errors addressed Originality – are the results new, and is prior work credited Significance – are the findings important or ground-breaking

What is the difference between repeatable and reproducible research?

Repeatable – can be repeated by the same scientists who carried it out Reproducible – can be reproduced by other teams of scientists

Around 1900, discoveries such as the electron and the gamma photon began to .......... with the existing models scientists held about the nature of matter.

Around 1900, discoveries such as the electron and the gamma photon began to conflict with the existing models scientists held about the nature of matter.

Name three pioneers of quantum theory credited with its early development.

Max Planck Niels Bohr Albert Einstein

True or False? A scientific claim should be trusted as soon as it is published in a journal, even before peer review.

False. Claims from research that has not been peer-reviewed should always be questioned, as there could be problems with the method, accuracy of results, or conclusions drawn.

A LevelPhysicsAQAFlashcardsParticles & RadiationEnergy Levels & Photon Emission

Energy Levels & Photon Emission (AQA A Level Physics): Flashcards

Exam code: 7408

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FrontCollisions of Electrons with Atoms
Define excitation.

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Cards in this collection (43)

Define excitation.
Excitation occurs when an electron absorbs a photon and gains enough energy to move up to a higher energy level.
Define de-excitation.
De-excitation occurs when an electron emits a photon and moves down to a lower energy level.
Define ionisation.
Ionisation occurs when an atom gains or loses an orbital electron and becomes charged.
What is the ionisation energy of an atom?
The minimum energy required to remove an electron from the ground state of an atom.
In a fluorescent tube, beam electrons .......... with electrons in mercury atoms, transferring kinetic energy.
In a fluorescent tube, beam electrons collide with electrons in mercury atoms, transferring kinetic energy.
In a fluorescent tube, what type of photon is emitted when excited mercury electrons de-excite back to the ground state?
Ultraviolet (UV) photons.
What happens to the UV photons emitted by mercury atoms in a fluorescent tube?
They collide with electrons in the phosphor coating, exciting them; these phosphor electrons then de-excite, emitting photons in the visible light range.
True or False?
An electron can only be removed from the ground state of an atom during ionisation.
False.
An electron can be removed from any energy level it occupies; the ionisation energy specifically refers to the minimum energy needed to remove an electron from the ground state.
Define ground state.
The ground state is the lowest energy level that an electron in an atom can occupy, corresponding to the most negative energy.
Define line spectrum.
A line spectrum is a series of discrete lines, at specific wavelengths, produced when excited atoms emit or absorb light; each element produces a unique line spectrum.
How does an emission spectrum appear?
A series of discrete coloured lines on a black background, each corresponding to a wavelength emitted when an electron transitions from a higher to a lower energy level.
How does an absorption spectrum appear, and how is it produced?
A continuous spectrum with dark lines at certain wavelengths, produced when white light passes through a cool, low-pressure gas; the missing wavelengths match the wavelengths present in the element's emission spectrum.
The energy of a photon emitted during an electron transition is equal to the .......... in energy between the two energy levels involved.
The energy of a photon emitted during an electron transition is equal to the difference in energy between the two energy levels involved.
What is the relationship between the energy difference of a transition and the wavelength of the emitted photon?
$Δ E = h f = \frac{h c}{λ}$
The larger the energy difference, the shorter the wavelength of the photon, and vice versa.
True or False?
Every element produces the same line spectrum, since all atoms contain electrons occupying energy levels.
False.
Each element produces a unique set of spectral lines, so elements can be identified from their line spectrum.
Define wave-particle duality.
Wave-particle duality is the phenomenon whereby light (and matter) can behave as both a particle and a wave, depending on the situation.
What evidence supports light behaving as a particle?
The photoelectric effect.
What evidence supports light behaving as a wave?
The diffraction and interference of light, for example in Young's double-slit experiment.
According to the photon model, why does the photoelectric effect only occur above a threshold frequency?
Each electron can absorb only a single photon, so only photons with a frequency above the threshold carry enough energy ( $E = h f$ ) to release a photoelectron.
What effect does increasing the intensity of light, above the threshold frequency, have on photoelectron emission?
More photoelectrons are emitted per second; the kinetic energy of the individual photoelectrons is unaffected.
A larger accelerating voltage .......... the diameter of the electron diffraction rings.
A larger accelerating voltage reduces the diameter of the electron diffraction rings.
What equation relates the kinetic energy of accelerated electrons to the accelerating voltage?
$E_{k} = \frac{1}{2} m v^{2} = e V$
True or False?
Wave theory correctly predicts that the kinetic energy of photoelectrons increases with the intensity of incident light.
False.
Wave theory predicts this, but it is not observed; increasing intensity above the threshold frequency increases the number of photoelectrons emitted, not their kinetic energy — this is why wave theory fails to explain the photoelectric effect.
Define the de Broglie wavelength.
The de Broglie wavelength is the wavelength associated with a moving particle, related to its momentum by $λ = \frac{h}{p}$
How does increasing the momentum of a particle affect its de Broglie wavelength?
The de Broglie wavelength decreases — the greater the momentum, the smaller the wavelength.
Using momentum $p = m v$ , the de Broglie equation can be written as $λ = \frac{h}{m v}$ , where m is the .......... of the particle.
Using momentum $p = m v$ , the de Broglie equation can be written as $λ = \frac{h}{m v}$ , where m is the mass of the particle.
What equation relates the de Broglie wavelength of a particle directly to its kinetic energy?
$λ = \frac{h}{\sqrt{2 m E}}$
In electron diffraction, what effect does increasing the speed (and momentum) of electrons have on the diffraction angle?
The angle of diffraction decreases.
True or False?
A proton and an electron accelerated through the same potential difference will have the same de Broglie wavelength.
False.
Since $λ \propto \frac{1}{\sqrt{m}}$ for equal kinetic energy, the more massive proton has a much shorter de Broglie wavelength than the electron.
Define electron diffraction.
Electron diffraction occurs when electrons passing through a slit similar in size to their de Broglie wavelength spread out, exhibiting wave-like behaviour.
What can the diffraction pattern of electrons passing through a crystalline solid be used to determine?
The structure of the crystal (arrangement of atoms) producing the pattern.
Why are high-energy electrons used to investigate the size of the atomic nucleus?
High-energy electrons have a shorter de Broglie wavelength, allowing much smaller structures, such as the nucleus, to be resolved.
Increasing the accelerating voltage increases the kinetic energy of electrons, which .......... their de Broglie wavelength.
Increasing the accelerating voltage increases the kinetic energy of electrons, which decreases their de Broglie wavelength.
How does increasing the kinetic energy of electrons affect the spacing of the diffraction rings observed?
The rings appear closer together, because the wavelength decreases as kinetic energy (and momentum) increase.
How is the radius of an electron diffraction pattern related to wavelength?
A longer wavelength produces a larger radius; a shorter wavelength produces a smaller radius.
True or False?
Electrons with a smaller momentum produce a sharper, more tightly-defined diffraction pattern.
False.
Electrons with smaller momentum have a longer de Broglie wavelength, which produces a larger radius and a more diffuse diffraction pattern, not a sharper one.
Define peer review.
Peer review is the process by which scientific claims published in journals are evaluated by other experts in the field before being accepted.
Name the three things scientists check for during peer review.
- Validity – is the method appropriate and are any errors addressed
- Originality – are the results new, and is prior work credited
- Significance – are the findings important or ground-breaking
What is the difference between repeatable and reproducible research?
- Repeatable – can be repeated by the same scientists who carried it out
- Reproducible – can be reproduced by other teams of scientists
Give an example of a phenomenon that could not be explained by the existing model of light, prompting scientists to develop wave-particle duality.
The photoelectric effect.
Around 1900, discoveries such as the electron and the gamma photon began to .......... with the existing models scientists held about the nature of matter.
Around 1900, discoveries such as the electron and the gamma photon began to conflict with the existing models scientists held about the nature of matter.
Name three pioneers of quantum theory credited with its early development.
- Max Planck
- Niels Bohr
- Albert Einstein
True or False?
A scientific claim should be trusted as soon as it is published in a journal, even before peer review.
False.
Claims from research that has not been peer-reviewed should always be questioned, as there could be problems with the method, accuracy of results, or conclusions drawn.

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