Quanta and Waves Flashcards
State what is meant by the term node in standing waves.
A point on the standing wave pattern where there is no disturbance or the amplitude is zero
Explain how coating glass in magnesium fluoride makes the surface non-reflecting despite light being reflected off both the glass and magnesium fluoride
Rays 1 and 2 interfere destructively.
What will happen to the spot spacing if the 650m laser is replaced with a 300m laser?
The spots will become closer together as angle decreases as lambda decreases.
State what is meant by the term antinode in standing waves
point of maximum amplitude disturbance
Explain how the value of the wavelength can be determined from this stationary wave pattern
Measure distance between adjacent nodes nodal distance and double this distance
6
It is not possible to know the (precise) momentum and position of a quantum particle simultaneously.
State one piece of evidence for the particle-like behaviour of waves.
Photoelectric effect
State one piece of evidence for the wave-like behaviour of particles.
Electron diffraction
A wave travelling along a string is represented by the relationship
y =9.50×10^-4 sin (922t-4.50x)
What is w?
w = 922 rads-1
A wave travelling along a string is represented by the relationship
y =9.50×10^-4 sin(922t-4.50x)
What is lambda?
450m
Explain what is meant by the uncertainty principle.
It is not possible to know the position and the momentum of a quantum particle simultaneously.
Not possible to know the lifetime of a quantum particle and the associated energy change simultaneously.
Explain what is meant by quantum tunnelling.
A quantum particle can exist in a position that, according to classical physics, it has insufficient energy to occupy.
State what is meant by SHM
Displacement is
proportional to and in the opposite direction to the acceleration/unbalanced
force.
State the effects of underdamping on SHM
Object oscillates back and forth around an equilibrium point, losing Energy each cycle until it comes to rest at equilibrium.
State the effects of critical damping on SHM
Quickest return to equilibrium position without oscillation
State the effects of overdamping on SHM.
Object experiences a large resistance to motion, taking a long time to reach the equilibrium position (if at all)
Explain how stationary waves are formed
Stationary waves are formed by a reflected wave interfering with an incident wave
Explain what is meant two coherent waves
Two waves are coherent if they have the same:
Speed, frequency, wavelength
A constant phase relationship
Explain what is meant by interference by division of amplitude
Each wave is being split, with some of it travelling along one path, and the remainder following a different path.
When these two parts are recombined, the difference in optical paths determines their phase difference, and hence how they interfere when they recombine.
Explain what is meant by interference by division of wavefront.
A wavefront is split into at least two parts which combine to form an interference pattern (e.g. Young’s Slits).
State what is meant by a plane polarised wave.
(The electric field vector)
oscillates (or vibrates) in one plane only.
Use the HUP to explain why alpha particles can be emitted from uranium nuclei when classical physics states that it cannot overcome the strong nuclear force holding it in place.
The momentum of the alpha particle is known precisely therefore its position is not known precisely.
There is a (small) probability that the particle could exist outside the nucleus (even although classically it does not have sufficient I energy to escape).
Laser light is directed through a double slit onto a screen. Explain how the pattern is produced.
Bright fringes due to constructive interference where waves are in phase/crest meets crest.
Dark fringes due to destructive interference where waves are totally out of phase/crest meets trough.
Describe the origin and composition of cosmic rays.
They are high-energy particles that come from space/ above the atmosphere/ are absorbed by the atmosphere.
Describe what is meant by the phrase energy is quantised.
Energy/radiation emitted/absorbec in discrete units (or, not continuous).
Explain qualitatively how the Bohr model of the atom can account for line emission spectra.
Electrons orbit the nucleus of an atom in only certain allowed orbits.
Charges between orbits can only produce discrete, fixed quanta of energy. Discrete frequencies produce discrete lines.
A driver is wearing polarising sunglasses. Explain how wearing polarising sunglasses rather than non-polarising sunglasses will reduce the glare experienced by the driver.
The polarising sunglasses will act as an analyser/ absorb/block (some of) the glare.
High energy charged particles are ejected from the Sun. State the name given to the constant stream of charged particles which the Sun ejects.
Solar wind
State 3 experiments that cannot be explained by classical physics.
- UV catastrophe
- Formation of emission and absorption spectra
- The photoelectric effect
State the key features of the Bhor model of the atom.
Electron energy and angular momentum are quantised.
