A photon is a massless discrete packet, or quantum , of electromagnetic energy .

What two experimental observations provide evidence that electromagnetic radiation behaves as particles?

The photoelectric effect Atomic line spectra

A photon transfers its energy not continuously, but as .......... packets of energy.

A photon transfers its energy not continuously, but as discrete packets of energy.

True or False? The energy carried by electromagnetic radiation is transferred gradually and continuously, rather than in discrete packets.

False. Each photon carries a specific amount of energy and transfers it all at once, rather than supplying it continuously.

How does the energy of a photon vary with the wavelength of the radiation?

Photon energy is inversely proportional to wavelength — a longer-wavelength photon has lower energy than a shorter-wavelength photon.

Einstein showed that a photon travelling in a vacuum has .......... , despite having no mass.

Einstein showed that a photon travelling in a vacuum has momentum , despite having no mass.

Define the electronvolt .

The electronvolt is the energy gained by an electron travelling through a potential difference of one volt .

To convert an energy from eV to J, .......... by 1.6 × 10 -19 .

To convert an energy from eV to J, multiply by 1.6 × 10 -19 .

True or False? The electronvolt is used because quantum-scale energies are typically much larger than one joule.

False. Quantum energies are typically much smaller than one joule, which is why the electronvolt is a more convenient unit.

A LevelPhysicsCambridge (CIE)Flashcards22. Quantum PhysicsEnergy & Momentum of a Photon

Energy & Momentum of a Photon (Cambridge (CIE) A Level Physics): Flashcards

Exam code: 9702

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FrontThe Photon
Define photon.
FrontThe Photon
What two experimental observations provide evidence that electromagnetic radiation behaves as particles?
BackThe Photon
The photoelectric effect
Atomic line spectra
FrontThe Photon
What wave phenomena does electromagnetic radiation exhibit that support classical wave theory?
BackThe Photon
Diffraction
Interference

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Cards in this collection (17)

Define photon.
A photon is a massless discrete packet, or quantum, of electromagnetic energy.
What two experimental observations provide evidence that electromagnetic radiation behaves as particles?
- The photoelectric effect
- Atomic line spectra
What wave phenomena does electromagnetic radiation exhibit that support classical wave theory?
- Diffraction
- Interference
A photon transfers its energy not continuously, but as .......... packets of energy.
A photon transfers its energy not continuously, but as discrete packets of energy.
True or False?
The energy carried by electromagnetic radiation is transferred gradually and continuously, rather than in discrete packets.
False.
Each photon carries a specific amount of energy and transfers it all at once, rather than supplying it continuously.
State the equation for the energy of a photon in terms of frequency.
$E = h f$
State the equation for the energy of a photon in terms of wavelength.
$E = \frac{h c}{λ}$
How does the energy of a photon vary with the wavelength of the radiation?
Photon energy is inversely proportional to wavelength — a longer-wavelength photon has lower energy than a shorter-wavelength photon.
State the equation relating a photon's momentum to its energy.
$p = \frac{E}{c}$
Einstein showed that a photon travelling in a vacuum has .........., despite having no mass.
Einstein showed that a photon travelling in a vacuum has momentum, despite having no mass.
True or False?
A particle must have mass to possess momentum.
False.
Photons are massless yet still carry momentum, related to their energy by $p = \frac{E}{c}$ .
Define the electronvolt.
The electronvolt is the energy gained by an electron travelling through a potential difference of one volt.
What is the value of 1 eV in joules?
$1 eV = 1.60 \times 10^{- 19} J$
To convert an energy from eV to J, .......... by 1.6 × 10^-19.
To convert an energy from eV to J, multiply by 1.6 × 10^-19.
State the equation relating the electronvolt to the kinetic energy gained by an electron accelerated from rest through potential difference V.
$e V = \frac{1}{2} m v^{2}$
State the equation for the speed of an electron accelerated from rest through a potential difference V.
$v = \sqrt{\frac{2 e V}{m}}$
True or False?
The electronvolt is used because quantum-scale energies are typically much larger than one joule.
False.
Quantum energies are typically much smaller than one joule, which is why the electronvolt is a more convenient unit.

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