A beam of α-particles is incident on a thin gold foil. Most α-particles pass straight through the foil.
A few are deflected by gold nuclei.
The diagram shows the path of one α-particle which passes close to a gold nucleus N in the foil.
The α-particle is deflected through an angle of 60° as it travels from A to B.
P marks its position of closest approach to the gold nucleus.
Sketch its path onto the diagram above.
[2]
Calculate the magnitude of the electrostatic force F between the α-particle (
) and the gold nucleus (
) when the α-particle is at P.
F = ......................................... N [4]
Show that the magnitude of the initial momentum of each α-particle is about 10–19 kg m s–1.
Take the mass of the α-particle to be 6.6 × 10–27 kg.
[3]
The gold nucleus N is initially at rest. During the passage of the α-particle from A to B, no other forces act on the two particles.
In the following questions label any relevant angles.
initial momentum at A
final momentum at B
[2]
Explain how you determined this momentum.
[2]
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