MCQ Detailed View

The Sun is the primary source of energy for the Earth and all life on it. This energy is produced in the core of the Sun through a process called nuclear fusion. Nuclear fusion is a reaction in which light atomic nuclei combine to form heavier nuclei, releasing a tremendous amount of energy in the form of heat and light.

In the Sun, the main fusion process is the fusion of hydrogen atoms into helium. Four hydrogen nuclei (protons) combine through a series of steps to produce one helium nucleus, along with energy, neutrinos, and positrons. The energy released in this process follows Einstein’s equation, E = mc², where a small amount of mass is converted into a large amount of energy. This energy then travels outward through radiation and convection zones and finally reaches the Sun’s surface to emit as sunlight.

Other options are incorrect:

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  Photoelectric emission (Option 1) is the emission of electrons from a material when light falls on it; it does not generate the Sun’s energy.

  
  


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  Nuclear fission (Option 2) is the splitting of heavy atomic nuclei into smaller nuclei, which is used in nuclear reactors, not stars like the Sun.

  
  


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  Thermionic emission (Option 4) is the release of electrons from a heated metal surface; it is unrelated to stellar energy production.

  
  

The energy generated by nuclear fusion in the Sun is responsible for daylight, solar heat, and the driving force of Earth’s climate and weather systems. It also powers photosynthesis in plants and sustains life on Earth.

In conclusion, the source of the Sun’s energy is nuclear fusion (Option 3), a natural process converting hydrogen into helium and releasing enormous amounts of energy. Understanding this process helps students link concepts of atomic physics, energy conversion, and astrophysics.

✅ Correct Answer: Nuclear fusion (Option 3)