After two hours one-eight of the starting amount of a certain radioactive isotope remained undecayed. The half-life of the isotope is

In a radioactive material the activity at time t₁, is A₁ and at a later time t₂, it is A₂. If the decay constant of the material is $$\lambda$$, then

A proton has kinetic energy E = 100 eV which is equal to that of a photon. The wavelength of photon is $$\lambda$$₂ and that of proton is $$\lambda$$₁. The ratio $${{{\lambda _2}} \over {{\lambda _1}}}$$ is proportional to

The radius of a muonic hydrogen atom is 2.5 $$\times$$ 10^$$-$$13 m. The total atomic volume (in m³) of a mole of such hydrogen atoms is (Take, $$\pi$$ = 3.14)