The half life of a radioactive substance is 20 minutes. In how much time, the activity of substance drops to of its initial value

Two nuclei have mass numbers A and B respectively. The density ratio of the nuclei is _____________.
Fill in the blank with the correct answer from the options given below.

The half-life of a radioactive sample undergoing α-decay is 1.4×10¹⁷ s. If the number of nuclei in the sample is 2.0×10²¹, the activity of the sample is nearly

In the nuclear emission stated above.
The mass number and atomic number of the product Q respectively, are:

Given below are two statements:
Statement I: Atoms are electrically neutral as they contain equal number of positive and negative charges.
Statement II: Atoms of each element are stable and emit their characteristic spectrum.
In the light of the above statements, choose the most appropriate answer from the options given below:

A radioactive nucleus undergoes spontaneous decay in the sequence Atomic number of element X. The possible decay particles in the sequence are:

In the given nuclear reaction, the element X is

A nucleus with mass number 240 breaks into two fragments each of mass number 120, the binding energy per nucleon of unfragmented nuclei is 7.6 MeV while that of fragments is 8.5 MeV. The total gain in the Binding Energy in the process is:

The half life of a radioactive substance is 20 minutes. In how much time, the activity of substance drops to of its initial value

Two nuclei have mass numbers A and B respectively. The density ratio of the nuclei is _____________.
Fill in the blank with the correct answer from the options given below.