Rutherfords Model and Alpha Scattering - UNSOLVED PRACTICE SET
Chapter: Structure of the Atom | Topic: Rutherfords Model and Alpha Scattering
RUTHERFORDS MODEL AND ALPHA SCATTERING - UNSOLVED PRACTICE SET
Topic: Rutherfords Model and Alpha Scattering
Multiple Choice Questions
Q1. In Rutherford's alpha scattering experiment, most alpha particles passed straight through the gold foil. This observation led to the conclusion that:
- The atom is a solid sphere
- Most of the atom is empty space
- The atom is positively charged throughout
- Electrons are embedded in a positive sphere
Q2. The alpha particles that were deflected back at angles greater than 90° suggested that:
- The atom has no nucleus
- The positive charge and mass are concentrated in a very small nucleus
- Electrons are heavy particles
- The gold foil was too thick
Q3. Rutherford's model of the atom is also called the:
- Plum pudding model
- Nuclear model
- Quantum model
- Wave model
Q4. According to Rutherford's model, electrons revolve around the nucleus in:
- Fixed circular paths
- Random paths
- Stationary positions
- Elliptical paths only
Q5. The main limitation of Rutherford's model was that it could not explain:
- The existence of the nucleus
- The scattering of alpha particles
- The stability of the atom and the line spectrum of hydrogen
- The discovery of electrons
Q6. In Rutherford's experiment, the source of alpha particles was:
- A cathode ray tube
- A radioactive source like radium
- An X-ray tube
- A laser
Short Answer Questions
Q7. Describe Rutherford's alpha scattering experiment with a simple diagram. What were the three main observations?
Q8. How did Rutherford interpret the observation that some alpha particles were deflected through large angles? What did this tell him about the structure of the atom?
Q9. Your school has a large open ground. Your teacher asks you to imagine that a cricket ball is the nucleus and the entire ground is the atom. Explain what this analogy teaches us about the structure of the atom according to Rutherford.
Q10. According to Rutherford's model, electrons revolve around the nucleus in circular paths. What problem did this create regarding the stability of the atom? Explain briefly.
Q11. Why did Rutherford use gold foil in his experiment? Could he have used aluminium foil instead? Give reasons.
Q12. Compare Thomson's model and Rutherford's model on the basis of: (i) distribution of positive charge, (ii) position of electrons, and (iii) size of the nucleus relative to the atom.
Long Answer Questions
Q13. Describe Rutherford's alpha scattering experiment in detail with a labelled diagram. Explain the three key observations and the conclusions drawn from each. How did this experiment lead to the nuclear model of the atom? What were the two major limitations of Rutherford's model?
Q14. A student performs a thought experiment: "If I shoot 10,000 alpha particles at a gold foil, and Thomson's model is correct, all particles should pass straight through with no deflection."
(a) Is the student's prediction correct for Thomson's model? Explain.
(b) What did Rutherford actually observe? Give approximate percentages.
(c) How did these actual observations disprove Thomson's model?
(d) Why did Rutherford say that the deflection of alpha particles was as surprising as "a 15-inch shell fired at a piece of tissue paper and coming back to hit you"?
Q15. "Rutherford's gold foil experiment is considered one of the most important experiments in the history of science." Discuss this statement by explaining: (i) the experimental setup and methodology, (ii) the unexpected results that changed atomic theory, (iii) how the nuclear model replaced the plum pudding model, and (iv) why this experiment is still relevant in modern physics research (such as in particle accelerators like CERN).
Numerical / Application-Based Problems
Q16. In Rutherford's experiment, alpha particles with a kinetic energy of 5 MeV (8 × 10⁻¹³ J) were fired at a gold foil.
(a) Calculate the velocity of an alpha particle. (Mass of alpha particle = 6.64 × 10⁻²⁷ kg)
(b) If the closest distance of approach of an alpha particle to the gold nucleus is 4 × 10⁻¹⁴ m, calculate the electrostatic potential energy at this distance. (Charge of alpha particle = +2e, charge of gold nucleus = +79e)
(c) What does this closest distance tell us about the size of the nucleus?
(d) If the diameter of a gold atom is 2.7 × 10⁻¹⁰ m, calculate how many times larger the atom is than the closest distance of approach.
Q17. A classroom simulation of Rutherford's experiment is conducted using a large circular board (representing the atom) and 100 small marbles (representing alpha particles).
(a) If 99 marbles pass straight through, 1 marble deflects slightly, and no marble bounces back, which model does this support — Thomson's or Rutherford's?
(b) To simulate Rutherford's actual results, how many marbles should pass straight through, how many should deflect slightly, and how many should bounce back? (Use approximate percentages)
(c) If the board has a diameter of 1 metre, and a small dot in the centre represents the nucleus, what should be the diameter of the dot to maintain the correct scale?
(d) Why is this simulation useful for understanding Rutherford's experiment, even though it is not exact?
Q18. Modern particle physics uses the same principle as Rutherford's experiment to probe the structure of protons and neutrons.
(a) Explain how the Large Hadron Collider (LHC) at CERN is like a giant Rutherford experiment.
(b) If protons are accelerated to 99.9% of the speed of light in the LHC, calculate their kinetic energy. (Mass of proton = 1.67 × 10⁻²⁷ kg, c = 3 × 10⁸ m/s)
(c) The discovery of the Higgs boson in 2012 was made by smashing protons together. How is this similar to Rutherford discovering the nucleus by scattering alpha particles?
(d) Why do you think India is investing in particle physics research, and how might it benefit Indian students and scientists?