Radioactivity — Prelims Questions

A radioactive sample has a half-life of $20,\text{s}$. If initially there are $N_0$ nuclei, how many nuclei will remain undecayed after $1,\text{minute}$?

Which of the following statements is INCORRECT regarding the properties of alpha, beta, and gamma radiations?

The decay constant of a radioactive isotope is $0.0231,\text{min}^{-1}$. What is its half-life?

A radioactive substance has an activity of $1000,\text{Bq}$ at time $t=0$. After $10,\text{s}$, its activity drops to $250,\text{Bq}$. What is the half-life of the substance?

In a beta-minus ($\beta^-$) decay process, which of the following changes occurs to the parent nucleus $_Z^A\text{X}$?

A radioactive nucleus undergoes a series of decays: one alpha decay and two beta-minus decays. If the initial nucleus is $_Z^A\text{X}$, what is the final nucleus?

Which of the following factors does NOT affect the rate of radioactive decay?