The count rate of a Geiger Muller counter for the radiation of a radioactive material of half-life 30 min decreases to 5 s-1 after 2 h. The initial count rate was.
20 s-1
25 s-1
80 s-1
625 s-1
The binding energy per nucleon is maximum in case of
2He4
26Fe56
56Ba141
92U235
Which of the following is used as a moderator in nuclear reactors?
Plutonium
Cadmium
Heavy water
Uranium
The activity of a radioactive sample is measured as 9750 counts/min at t = 0 and as 975 counts/min at t = 5 min. The decay constant is approximately
0.922/min
0.691/min
0.461/min
0.230/min
Energy released in the fission of a single 92U235 nucleus is 200 MeV. The fission rate of a 92U235 filled reactor operating at a power level of 5 W is
1.56 x 10-10 s-1
1.56 x 1011 s-1
1.56 x 10-16 s-1
1.56 x 10-17 s-1
Which of the following statements is true for nuclear forces?
They obey the inverse square law of distance.
They obey the inverse third power law of distance.
They are short range forces.
They are equal in strength to electromagnetic forces.
The stable nucleus that has a radius half that of Fe56 is
Li7
Na21
S16
Ca40
The average binding energy of a nucleon inside an atomic nucleus is about
8 MeV
8 eV
8 J
8 erg
In the nucleus of 11Na23, the number of protons, neutrons and electrons are
11,12,0
23,12,11
12,11,0
23,11,12
Atomic weight of boron is 10.81 and it has two isotopes and . Then, the ratio of atoms of and in nature would be
19 : 81
10 : 11
15 : 16
81 : 19
