Half-life of radioactive sample is 24 h . If a newly prepared radioactive sample shows 4 times the allowed and safe value of radio activity, the minimum time after which one can work safely with the source is

The binding energy (BE) per nucleon for an element is 7.14 MeV . If the BE of element is 28.6 MeV , then the number of nucleons in the element is

Let $G, W, E$ and $S$ be relative strength of gravitational, weak-nuclear, electromagnetic and strong-nuclear forces, respectively. Which of the correct statement?

In the Bohr model an electron of mass $m$ moves in a circular orbit around the proton. Considering the orbiting electron to be a circular current loop, the magnetic moment of the hydrogen atom, when the electron is in $n$th excited state. (Assume, $h=$ Planck's constant)