Page 250 - Physics Coursebook 2015 (A level)

Cambridge International AS Level Physics
9 Geiger and Marsden carried out an experiment to investigate the structure of the atom. In this experiment α-particles were scattered by a thin film of gold.
a When Rutherford analysed their results, what conclusions did he draw about the distribution
of mass and charge in the atom? [2]
b Describe and explain the experimental observations that led to these conclusions. [3]
10 Beta decay occurs as either β+-decay or β−-decay. An isotope of calcium 46Ca decays by 46 23 20
β-emission into the isotope 21Sc, and an isotope of magnesium 12Mg decays by β-emission into the isotope 23Na.
11
a Copy and complete the following decay equations for the calcium and magnesium isotopes.
i decay of calcium: 46Ca → ...e + ...Sc+ + ... 20 ... ...
ii decay of magnesium: 23Mg → ...e + ...Na+ + ... [3] 12 ... ...
b State what happens in each type of β-decay in terms of the quark model of nucleons.
i β−-decay [1] ii β+-decay. [1]
c Name the force responsible for β-decay. [1]
[2]
11 a
b A proton and a neutron each contain three quarks, either up or down quarks.
A quark is a fundamental particle but a neutron is not. Explain what this statement means.
i Copy and complete the table to show the charge on a proton and a neutron and the quarks that they contain.
proton
neutron
Charge
Quarks
ii Using information from your table, suggest why some quarks must have a positive charge
and some quarks a negative charge. [2] c State what interaction is responsible for holding the nucleus together. [1]
d When a neutron decays it produces an electron and two other particles. Copy and complete the
decay equation for a neutron.
10 n → [2]
e The electron and the neutron belong to different groups of particles.
Copy and complete the table to show the group of particles to which the electron and neutron belong and state the name of another member of each group.
electron
neutron
[2]
Group to which it belongs
Another particle in the same group
238