Question 17N.2.HL.TZ0.3
| Date | November 2017 | Marks available | [Maximum mark: 15] | Reference code | 17N.2.HL.TZ0.3 |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Determine, Draw, Explain, Outline, Plot, State | Question number | 3 | Adapted from | N/A |
The Feynman diagram shows electron capture.
State and explain the nature of the particle labelled X.
[3]
«electron» neutrino
it has a lepton number of 1 «as lepton number is conserved»
it has a charge of zero/is neutral «as charge is conserved»
OR
it has a baryon number of 0 «as baryon number is conserved»
Do not allow antineutrino
Do not credit answers referring to energy
Particles can be used in scattering experiments to estimate nuclear sizes.
Outline how these experiments are carried out.
[2]
«high energy particles incident on» thin sample
detect angle/position of deflected particles
reference to interference/diffraction/minimum/maximum/numbers of particles
Allow “foil” instead of thin
Outline why the particles must be accelerated to high energies in scattering experiments.
[3]
λ OR λ
so high energy gives small λ
to match the small nuclear size
Alternative 2
E = hf/energy is proportional to frequency
frequency is inversely proportional to wavelength/c = fλ
to match the small nuclear size
Alternative 3
higher energy means closer approach to nucleus
to overcome the repulsive force from the nucleus
so greater precision in measurement of the size of the nucleus
Accept inversely proportional
Only allow marks awarded from one alternative
State and explain one example of a scientific analogy.
[2]
two analogous situations stated
one element of the analogy equated to an element of physics
eg: moving away from Earth is like climbing a hill where the contours correspond to the equipotentials
Atoms in an ideal gas behave like pool balls
The forces between them only act during collisions
Electron diffraction experiments indicate that the nuclear radius of carbon-12 is 2.7 x 10–15 m. The graph shows the variation of nuclear radius with nucleon number. The nuclear radius of the carbon-12 is shown on the graph.
Determine the radius of the magnesium-24 nucleus.
[2]
R = 2.7 x 10–15 x
3.4 – 3.5 x 10–15 «m»
Allow use of the Fermi radius from the data booklet
Plot the position of magnesium-24 on the graph.
[1]
correctly plotted
Allow ECF from (d)(i)
Draw a line on the graph, to show the variation of nuclear radius with nucleon number.
[2]
single smooth curve passing through both points with decreasing gradient
through origin
