MCQ Detailed View

Radioactivity is the phenomenon in which unstable atomic nuclei release energy in the form of radiation. This groundbreaking discovery was made by Henri Becquerel in 1896, marking a major milestone in the field of physics and chemistry.

Becquerel’s discovery happened accidentally while he was experimenting with fluorescent materials and photographic plates. He wanted to study if sunlight could make certain substances emit X-rays. He wrapped a photographic plate in black paper, placed a uranium salt crystal on top, and stored it in the dark. Surprisingly, even without exposure to sunlight, the plate was fogged as if it had been exposed to light. This revealed that uranium emitted invisible rays on its own. This phenomenon was later named radioactivity.

Radioactivity is caused by the instability of atomic nuclei. Atoms of radioactive elements (like uranium or radium) spontaneously emit alpha particles, beta particles, or gamma rays to reach a more stable state. This process releases a significant amount of energy and can transform one element into another over time.

Other scientists played major roles in advancing this discovery:

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  Marie and Pierre Curie later isolated new radioactive elements such as polonium and radium.

  
  


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  Ernest Rutherford studied radiation types and developed the nuclear model of the atom.

  
  

The other options in this question do not apply:

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  Lord Kelvin contributed to thermodynamics, not radioactivity.

  
  


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  J.J. Thomson discovered the electron.

  
  


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  Ernest Rutherford studied radioactivity but did not discover it.

  
  

This question belongs to Physics, specifically nuclear physics, as it relates to the natural emission of energy from unstable atoms. Henri Becquerel’s work opened the door to nuclear science, leading to advancements in medicine, energy production, and atomic research.