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Rutherford devised an experiment to fire alpha particles at thin gold foil - Edexcel - GCSE Physics - Question 8 - 2022 - Paper 1
Question 8
Rutherford devised an experiment to fire alpha particles at thin gold foil. It was found that alpha particles were scattered by the gold foil. The gold foil was 4.0... show full transcript
Worked Solution & Example Answer:Rutherford devised an experiment to fire alpha particles at thin gold foil - Edexcel - GCSE Physics - Question 8 - 2022 - Paper 1
Step 1
Estimate how many gold atoms would fit across this thickness of gold foil.
Answer
To estimate the number of gold atoms that fit across the thickness of the gold foil, we first convert the thickness to nanometers:
- Thickness of gold foil = 4.0 × 10⁻⁷ m = 4.0 × 10² nm
Next, we know that a gold atom has a diameter of approximately 0.5 nm.
To find the number of atoms across the foil's thickness, we divide the thickness of the foil by the diameter of a gold atom:
Therefore, approximately 800 gold atoms fit across the thickness of the gold foil.
Step 2
Estimate the ratio of the number of particles scattered through 5° to the number of particles scattered through 100°.
Answer
From the graph in Figure 11, observe the number of particles scattered at 5° and 100°:
- Particles scattered at 5° is approximately 100.
- Particles scattered at 100° is approximately 0.3.
The ratio is:
Thus, the estimated ratio of the number of particles scattered through 5° to the number scattered through 100° is approximately 333.33.
Step 3
Explain how the difference in the number of particles scattered at different angles gives evidence for the current model of the structure of the atom.
Answer
The difference in the number of particles scattered at various angles provides crucial evidence for the nuclear model of the atom:
- Scattering at Small Angles: A large number of alpha particles are scattered at small angles, indicating that most of the atom is empty space, allowing particles to pass through.
- Scattering at Large Angles: However, a small fraction of particles are deflected at large angles, suggesting that these particles encounter a concentrated mass within the atom, specifically the nucleus.
- Conclusion: This supports the idea that the majority of an atom's mass is in a tiny nucleus at the center, with electrons orbiting in the surrounding space, confirming the structure of the atom as described by the current model.
Step 4
Describe how the students could use the apparatus to model the scattering of alpha particles.
Answer
To model the scattering of alpha particles using the apparatus shown in Figure 12:
- Setting Up: Position the large sheet of paper horizontally and ensure that the lines on the paper are accurately spaced at 1 cm apart.
- Creating the Slope: Set the movable slope to allow a marble to roll down towards the paper.
- Simulating Alpha Particles: As the marble rolls down, it simulates the alpha particles being fired at the target. The angle at which the marble hits the surface can be adjusted to mimic different scattering angles.
- Observation: Students can then observe how the marble (representing the alpha particles) behaves as it strikes the paper, noting changes in direction similar to how alpha particles are scattered by gold atoms.
Step 5
Give one limitation of this model.
Answer
One limitation of this model is that it oversimplifies the interactions between alpha particles and atoms. In reality, alpha particles may undergo complex interactions not accounted for by a simple rolling marble simulation. Additionally, the scale of the marble and the paper does not accurately represent atomic dimensions, potentially leading to misunderstandings about the behavior of subatomic particles.