A radioactive sample contains 1600 nuclei and has a half-life of 8 days. How many undecayed nuclei remain after 32 days?
Answer and explanation
Correct answer: A. 100
- Step 1: 32 days is 4 half-lives.
- Step 2: Each half-life halves the number of nuclei: 1600 / 2^4 = 100.
Answer
100.
Why not the others: Decay is exponential: the number is halved each half-life, not reduced by a fixed amount; using one half-life too few leaves too many nuclei.
Practise more Waves, optics and nuclear physics.
Free questions with an explanation for every one, and full timed Državna Matura (Montenegro) mock tests.
More Waves, optics and nuclear physics questions
- A ray in air strikes a transparent material at 90 degrees to the normal and is refracted at 30 degrees. What is the refractive index of the…
- A wave has frequency 5 Hz and wavelength 0.1 m. What is its speed?
- A radioactive sample contains 1200 nuclei and has a half-life of 12 days. How many undecayed nuclei remain after 36 days?
- A wave has frequency 440 Hz and wavelength 4 m. What is its speed?