Modern Physics Test - 5

A radioactive substance has a half-life of four months. Three-fourth of the substance will decay in

C¹⁴ has half-life 5700 yr. At the end of 11400 yr, actual amount left is

²⁰⁸Ra has half-life 120 days. The amount of ²⁰⁸Ra, if the activity level is one mCi

The counting rate observed from a radioactive source at t=0s was 1600 counts/s^-1, and at t = 8s it was 100 count/s^-1. The counting rate observed at t=6s was

Mean life of a radioactive sample is 100s. Then, its half-life (in minute) is

If parent decays to daughter nucleus with a rate r and daughter nucleus has average life τ and number of nuclei of daughter nucleus at any instant is N, then for radioactive equilibrium to be achieved, we have

In a specific case, angular momentum is an even integral multiple of h/2π. The longest possible wavelength emitted by hydrogen in visible region in such a world, according to Bohr’s model is

If the binding energies of a deuteron and an α-particle are 1.125 MeV and 7.2 MeV, respectively. Then, the more stable of the two is

The nuclei of which one of the following pairs of nuclei are isotones?

In the nuclear reaction,

the atomic mass and atomic number of P are, respectively