Answer: Fast electrons suddenly decelerate hitting a metal target.
- A Slow electrons gently strike a metal target at low speed
- B Fast electrons suddenly decelerate hitting a metal target
- C Protons are accelerated and strike a heavy metal target
- D Ultraviolet light is incident on a metal surface
Correct answer: B. Fast electrons suddenly decelerate hitting a metal target
Explanation: X-rays (Bremsstrahlung) are produced when fast electrons abruptly decelerate in a metal target, converting KE to X-ray photons.
The Geiger–Marsden alpha-scattering result: a few alpha particles bounce back at large angles, which rules out Thomson’s diffuse model and demands a tiny, massive, positively charged nucleus. Image: Kurzon, CC BY 3.0, via Wikimedia Commons.
Concept context
Thomson's plum-pudding model, Rutherford's nuclear model from alpha-scattering, Bohr's postulates and hydrogen spectrum, spectral series (Lyman to Pfund), Rydberg formula, and limitations of each model.