Half-life of a radioisotope is 4 × 10⁸ years. If there are 10³ radioactive nuclei in a sample today, the number of such nuclei in the sample 4 × 10⁹ years ago were

Which one of the following disintegration series of the heavy elements will give ²⁰⁹Bi as a stable nucleus?

The lifetime of an atomic state is 1ns. The natural line width of the spectral line in the emission spectrum of this state is of the order of

The quark content of $$\sum {^ + } ,\,{K^ - },\,{\pi ^ - }$$   and p is indicated: $$\left| {\sum {^ + } } \right\rangle = \left| {uus} \right\rangle ;\,\left| {{K^ + }} \right\rangle = \left| {s\overline u } \right\rangle ;\,\left| \pi \right\rangle = \left| d \right\rangle ;\,\left| p \right\rangle = \left| {uud} \right\rangle $$
In the process, $${\pi ^ - } + p \to {K^ - } + \sum {^ + } ,$$     considering strong interactions only, which of the following statements is true?

The four possible configurations of neutrons in the ground state of $${}_4^9Be$$  nucleus according to the shell model, and the associated nuclear spin are listed below. Choose the correct one