A-level Physics : Nuclear Reactions

Rutherford's original aim of the experiment was to verify the Plum Pudding Model for the atom.

Which of the following results did Rutherford expect to observe when he first conducted his Gold Foil experiment based on the Plum Pudding Model?

• All alpha particles would be able to pass through the gold foil with little or no angular deflection
• The gold foil will be able absorb the alpha particles.
• A small fraction of the alpha particles (1 in 8000) will suffer large deflections of more than 90 degrees with some having deflections as large as 180 degrees.
• A small fraction of alpha particles would pass through, with most being absorbed by the gold foil or deflected by the positively charged gold atom.

When the experiment was conducted, some key observations were however made. Which of the following are the observations?

• Most of the alpha particles were absorbed and trapped by the gold foil
• Most of the alpha particles were deflected backwards or suffered large angular deflections of greater than 90 degrees or came straight back.
• Most of the alpha particles passed through undeviated or had very small angular deflection.
• A very small fraction (~ 1 in 8000) of the alpha particles passed through the gold foil undeviated.

The observations made in the Rutherford's Alpha Scattering experiment produced new insights into the structure of the atom.

Which conclusions can be drawn from the results of the experiment?

• Electrons orbit the atomic nucleus.
• The size or volume of the nucleus is very small compared to the atom.
• The protons were concentrated in a very small volume in the centre of the atom called the nucleus.
• Most of the atom is empty space.
• The mass of the atom is concentrated in a very small volume within the atom.

[UCLES N95/I/28]

In repeating Rutherford's α-particle scattering experiment, a student used the apparatus shown, in a vacuum, to determine n, the number of α-particles incident per unit time on a detector held at various angular positions θ.

Which graph best represents the variation of n with θ?

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[UCLES N05/I/39]

Two α-particles with equal energies are fired towards the nucleus of a gold atom.Which diagram best represents their paths?

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• Option A
• Option B
• Option C
• Option D

[CIE 9702 Nov 2002 P1 Q38]

The numbers of protons, neutrons and nucleons in three nuclei are shown.

Which nuclei are isotopes of the same element?

• X and Y

• X and Z

• Y and Z

• None

[CIE 9702 Nov 2007 P1 Q37]

What need not be conserved in nuclear reactions?

• energy and mass
• nucleon number
• proton number
• neutron number
• linear momentum