2A Flashcards
Describe what quantum mechanics is
Quantum mechanics explains the Physics behind anything which cannot be explained by classical Physics (blackbody radiation, the photoelectric effect, emission and absorption spectra, atomic structure and electron diffraction).
State what is meant by ‘wave-particle duality’
Under certain conditions particles can behave like waves and waves can behave like particles.
State an example of light behaving as a particle.
Photoelectric effect.
State an example of light behaving as a wave.
Youngs’ double slits.
State an example of particles (electrons) behaving as a particle.
Cathode ray tube.
State an example of particles (electrons) behaving as a wave.
Electron microscope.
Explain why the de Broglie wavelength is important.
For a particle to exhibit wave like properties its de Broglie wavelength must be of
comparable size to the object which it scatters from.
Describe what is meant by black body radiation.
The amount of radiation emitted at a given frequency or wavelength depends on
temperature not on the type of material.
Explain how the photoelectric effect works.
High energy photons cause the ejection of electrons from metals. Increasing the energy of
the photons increases the energy of the ejected electrons. Increasing the number of the
photons increases the number of ejected electrons.
Describe what is meant by the phrase ‘energy is quantised’.
Energy is emitted or absorbed in discrete packets and is not continuous.
Explain how the Bohr model of the atom accounts for line emission spectra.
Electrons orbit in discrete energy levels. Transitions between then levels emit photons of
discrete/fixed energies.
Explain the Heisenberg uncertainty principle.
To measure one value precisely (momentum or energy) it means we are unable to measure
a second value precisely (position or time).
Explain what quantum tunnelling is.
When a particle needs to get over a potential hill it looks impossible through classical
Physics. Using quantum tunnelling it is possible, although not probable that a certain
percentage of particles can overcome the hill by tunnelling. This is how alpha decay works
and how a scanning tunnelling microscope works.
State what a ‘solar wind’ is.
Charged particles released from the sun.
Explain why comet tails always face away from the sun.
The solar wind from the sun blows the comet debris (tail) away from it.
