Atoms and Nucle...

The nuclide ¹³¹I is radioactive, with a half-life of 8.04 days. At noon on January 1, the activity of a certain sample is 600 Bq. activity at noon on January 24 will be

U²³⁸ decays into Th²³⁴ by the emission of an α– particle. There follows a chain of further radioactive decays, either by α–decay or by β–decay. Eventually a stable nuclide is reached and after that, no further radioactive decay is possible. Which of the following stable nuclides is the end product of the U²³⁸ radioactive decay chain

If the mass of a radioactive sample is doubled, the activity of the sample and the disintegration constant of the sample are respectively

At a given instant there are 25% undecayed radioactive nuclei. After 10 s the number of undecayed nuclei reduces to 6.25%, the mean life of the nuclei is

The ratio of ionization energy of Bohr\'s hydrogen atom and Bohr\'s hydrogen like lithium atom is

Consider a hypothetical annihilation of a stationary electron with a stationary positron. What is the wavelength of resulting radiation
(h = Planck\'s constant, c = speed of light, m₀ = rest mass)

In a sample of hydrogen like atoms all of which are in ground state, a photon beam containing photons of various energies is passed. In absorption spectrum, five dark lines, are observed. The number of bright lines in the emission spectrum will be (assume that all transitions takes place)

A hydrogen atom emits a photon corresponding to an electron transition from n = 5 to n = 1. The recoil speed of hydrogen atom is almost (mass of proton ≈ 1.6 × 10^–27 kg)

Number of nuclei of a radioactive substance at time t = 0 are 1000 and 900 at time t = 2 s. Then number of nuclei at time t = 4 s will be

The ratio between total acceleration of the electron in singly ionized helium atom and hydrogen atom (both in ground state) is