Physics Simulation Atomic Physics & Structure

Rutherford's Alpha Particle Scattering Experiment (1911)

Gun Position: Y = 140px (Straight Path)
Particles Fired: 0
💡 Nuclei occur at regular 60px intervals (Y = 80, 140, 200, 260, 320). Deflection zone is ultra-narrow (±3px)!
Beam:
Undeflected / Tiny ($<10^\circ$)
0
~99.8% of particles
Moderate ($10^\circ - 90^\circ$)
0
Rare deflections
Large / Backscatter ($>90^\circ$)
0
~1 in 8,000 rebound!
Ernest Rutherford's Astonishment (1911):

"It was quite the most incredible event that has ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you!"

Inquiry & Deductions Questionnaire

Core Discovery

Drag the alpha source directly to probe the foil. Analyze what can—and cannot—be deduced from these scattering observations.

1. More than $99\%$ of the alpha particles passed straight through the gold foil undeflected. What direct conclusion did Rutherford deduce from this?

2. A tiny fraction of alpha particles (about $1$ in $8,000$) were deflected through angles larger than $90^\circ$ (backscattered). What does this require?

3. Which of the following CANNOT be deduced from the alpha particle scattering experiment alone?

4. Can Rutherford's scattering experiment explain why orbiting electrons do not continuously radiate electromagnetic energy and spiral into the nucleus?

5. Why must the entire alpha particle scattering apparatus be placed inside an evacuated chamber (vacuum)?

6. If J.J. Thomson's "plum pudding" model of the atom were correct, what would have been observed in this experiment?