Ba-122 has half-life of 2 min. Experiment has to be done using Ba-122 and it takes 10 min to set up the experiment. It initially 80 g at Ba-122 was taken, how much Ba was left when experiment was started?

When the speed of light becomes $$\frac{2}{3}$$ of its present value, then the energy released in a given atomic explosion would

An electron of an atom transits from $$n_1$$ to $$n_2$$. In which of the following maximum frequency of photon will be emitted?

Two protons are kept at a separation of 40 $$\mathop A\limits^o $$. F$$_n$$ is the nuclear force and F$$_e$$ is the electrostatic force between them. Then,