A radioactive material decays by simultaneous emissions of two particles with half lives of $1400\, years$ and $700\, years$ respectively. What will be the time after which one third of the material remains? (Take In $3=1.1$ ) (In $years$)

The half life of a radioactive substance against $\alpha  - $ decay is $1.2 \times 10^7\, s$. What is the decay rate for $4.0 \times 10^{15}$ atoms of the substance

If a radioactive substance reduces to $\frac{1}{{16}}$ of its original mass in $40$ days, what is its half-life .........$days$

A sample of radioactive element containing $4 \times 10^{16}$ active nuclei. Half life of element is $10$ days, then number of decayed nuclei after $30$ days is  ........ $\times 10^{16}$ 

A radioactive sample has an average life of $30\, {ms}$ and is decaying. A capacitor of capacitance $200\, \mu\, {F}$ is first charged and later connected with resistor $^{\prime}{R}^{\prime}$. If the ratio of charge on capacitor to the activity of radioactive sample is fixed with respect to time then the value of $^{\prime}R^{\prime}$ should be $....\,\Omega$

If half-life of a substance is $3.8\, days$ and its quantity is $10.38\, gm$. Then substance quantity remaining left after $19\, days$ will be ........$gm$