Mass is lost in nuclear fusion because a portion of the mass of the original nuclei is converted into energy, in accordance with Einstein's famous equation, E=mc². This energy is then released during the fusion process.
Here's a breakdown of the process:
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Fusion Reaction: In nuclear fusion, two or more light atomic nuclei combine, or "fuse," to form a single, heavier nucleus.
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Mass Defect: The crucial point is that the mass of the resulting nucleus is less than the sum of the masses of the original nuclei. This difference in mass is called the "mass defect."
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Energy Release: The mass defect isn't simply lost; it's converted into energy. This conversion follows Einstein's mass-energy equivalence principle (E=mc²), where:
- E = Energy released
- m = Mass defect (mass lost)
- c = Speed of light (a very large number)
Because the speed of light (c) is such a large number, even a small amount of mass converted results in a tremendous release of energy. This is why nuclear fusion is such a powerful energy source.
- Binding Energy: This phenomenon is related to the concept of nuclear binding energy. The resulting heavier nucleus is more tightly bound (has a higher binding energy per nucleon) than the original nuclei. This greater binding energy corresponds to a lower overall mass.
In simpler terms:
Imagine you're building a LEGO structure.
- You start with individual LEGO bricks (the original nuclei).
- You combine them to build a larger structure (the new nucleus).
- During the process of connecting the bricks, a tiny bit of material "disappears" and transforms into the energy that holds the structure together stronger.
- The completed structure weighs (has mass) slightly less than the sum of the weights of the individual bricks.
Example:
Consider the fusion of hydrogen isotopes (Deuterium and Tritium) into Helium:
Deuterium (²H) + Tritium (³H) → Helium (⁴He) + Neutron (n) + Energy
The combined mass of Deuterium and Tritium is slightly more than the combined mass of Helium and the neutron. This "missing mass" is released as a substantial amount of energy.
In conclusion, mass loss in nuclear fusion is not a disappearance of matter, but a conversion of mass into energy, dictated by E=mc², contributing to the binding energy of the new nucleus and resulting in a release of tremendous energy.
