The nucleus
Fission splits a heavy nucleus and fusion joins two light ones; both release energy because what is left weighs a little less than what went in, and that missing mass comes out as energy. That is E = mc², and since the speed of light squared is enormous, a scrap of mass gives an absurd amount of energy. An unstable nucleus decays at a rate that cannot be sped up or slowed down: every half-life leaves half of what was there, never quite zero, which is why waste is measured in half-lives.
Where this sits
- Comes after
- Radiation
Exercises from this rung
Generated by the app, from easiest to hardest
What is fusion?
- Two small nuclei join
- Two molecules combine
- A big nucleus splits
- An atom loses an electron
Why Fission splits a heavy nucleus, like uranium, and it is what happens in a nuclear plant. Fusion joins two light ones, like hydrogen, and it is what happens in the Sun. Both release energy because the result weighs a little less than what went in, and that missing mass comes out as energy.
easierWhat is fission?
- Two small nuclei join
- Two molecules combine
- An atom loses an electron
- A big nucleus splits
Why Fission splits a heavy nucleus, like uranium, and it is what happens in a nuclear plant. Fusion joins two light ones, like hydrogen, and it is what happens in the Sun. Both release energy because the result weighs a little less than what went in, and that missing mass comes out as energy.
in betweenA material has a half-life of 50 years. What percentage is left after 150 years?
Answer 12.5
Why Every 50 years half of what was there is left: 3 half-lives give 50 → 25 → 12.5%. It never quite reaches zero, only approaches it, which is why nuclear waste is measured in half-lives and not in expiry dates.
harder