Why radioactive decay is random, the meaning of half-life, interpreting decay curves, solving half-life problems, and applications such as tracers, medical treatment and carbon dating.
5 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.
Radon gas in a basement and carbon dating of an ancient bone both rely on half-life: how long it takes for half of a radioactive sample to decay.
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
Copy these into your notebook in your own words — that is how they stick.
Unpredictable for a single nucleus; predictable for large numbers.
Not affected by temperature, pressure or chemical state.
Time for half the nuclei to decay (or the count rate to halve).
The same for any amount of the isotope.
(½)ⁿ with n = t ÷ T½.
Exponential: use more than one pair of values.
Tracers, radiotherapy, sterilising, smoke alarms, thickness gauges, carbon dating.
C-14 half-life 5 730 years.
3 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness. More games in the Physics Arcade.
8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better. Work each item on paper first.
Write full answers, then reveal the mark scheme and tick the points you earned (15 marks in total). Show all your working — method marks count. Your answers are saved on this device.
Question 1 [15 marks]
The mass of a radioactive isotope in a sample is 80 g at t = 0 and falls to 40 g after 6.0 days.
(a) (a) Define half-life. [2]
(b) (b) State the half-life of the isotope. [1]
(c) (c) Calculate the mass of the isotope remaining after 24 days. [3]
(d) (d) Determine the time taken for the mass to fall to one-sixteenth of its original value. [3]
(e) (e) State whether heating the sample would change its half-life, with a reason. [2]
(f) (f) State two uses of radioisotopes. [2]
(g) (g) State how a smaller sample would change the activity readings. [2]
Find these in your own past-paper booklets for extra timed practice. Items above are written in the style of these papers; any adapted from a specific question say so.