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Rutherford devised an experiment to fire alpha particles at thin gold foil - Edexcel - GCSE Physics: Combined Science - Question 5 - 2022 - Paper 1
Question 5
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: Combined Science - Question 5 - 2022 - Paper 1
Step 1
Estimate how many gold atoms would fit across this thickness of gold foil.
Answer
To determine how many gold atoms fit across the thickness of the gold foil, we can start by calculating the thickness of the foil in nanometers:
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Convert the thickness from meters to nanometers:
.
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Calculate how many gold atoms fit into the thickness:
= rac{4.0 imes 10^{2} ext{ nm}}{0.15 ext{ nm}} = rac{400}{0.15} ext{ atoms} \ \ ext{Number of atoms} \ = 2666.67 \ \ \ = 2700 \text{ (rounded)}.$
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 7:
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Estimate the number of particles scattered through 5°. Based on the graph, it appears to be around .
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Estimate the number of particles scattered through 100°. From the graph, it appears this value is about .
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Thus the ratio is:
= \frac{10^{6}}{10^{2}} = 10^{4} \ \text{Ratio} = 10,000.
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 scattering of alpha particles at different angles provides crucial insights into the structure of the atom:
- Observations: Most alpha particles pass straight through the gold foil with little deflection, indicating that atoms are mostly empty space.
- Deflections: Some alpha particles are scattered at small angles (less than 90°), suggesting that there are forces at play within the atom, likely from nearby nuclei.
- Rebounds: Very few alpha particles are scattered at large angles (greater than 90°), which implies that these particles are encountering a dense, positively charged nucleus within the atom.
- Conclusions: This supports the model that atoms consist of a small, dense nucleus surrounded by a cloud of electrons, affirming the understanding that an atom is mostly empty space, with a concentrated area of mass in the nucleus.
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:
- Position the movable slope at a height and allow the marble to roll down towards the large sheet of paper.
- As the marble (representing an alpha particle) hits the paper (representing the gold foil), observe how it scatters in various directions.
- Students can record the angles of scattering by using the protractor placed on the paper.
- By varying the initial angle of the slope, students can simulate different scenarios of how alpha particles interact with the foil.
Step 5
Give one limitation of this model.
Answer
One limitation of this model is that it does not accurately represent the scale and interaction forces of real alpha particles and gold atoms. Unlike the solid marble, alpha particles are much smaller and can interact differently with the atomic structure, including repulsion and other quantum effects that are not captured in this physical model.