The Decay Constant Of A Radioactive Sample is . The Half-life And Mean-life Of The Sample Are (respectively) Given By :

In the equation     

           ,  

The correct symbol for X is

The kinetic energy of a 300 K thermal neutron is

The energy released by the fission of one uranium atom is 200 MeV. The number of fissions per second required to produce 3.2 W of power is

The binding energy of deuteron  is 1.15 MeV per nucleon and an alpha particle  has a binding energy of 7.1 MeV per nucleon. Then in the reaction 

the energy Q released is 

What is the rest mass energy of an electron?

After two hours  of the initial amount of a certain radioactive isotope remains undecayed. The half life of the isotope is  

The half life of a certain radio isotope is 10 minutes. The number of radioactive nuclei at a given instant of time is 10⁸. Then the number of radioactive nuclei left 5 minutes later would be

The half life of Pa – 218 is 3 minutes. What mass of a 16 g sample of Pa – 218 will remain after 15 minutes?

A freshly prepared radioactive source of half life 2 h emits radiation of intensity which is 64 times the permissible safe level. The minimum time after which it would be possible to work safety with this source is  

The radioactive decay of an element X to elements Y and K is represented by the equation  

The sequence of the emitted radiations is