Which one of the following is used as a moderator in nuclear reaction?
Uranium
Heavy water
Cadmium
Plutonium
The K line from molybdenum (atomic number = 42) has a wavelength of 0.7078 . The wavelength of K line of zinc (atomic number = 30) will be
1
1.3872
0.3541
0.5
B.
1.3872
Decay constant of radioactive element is 1.5 × 10-9/s. Average age of element is
1.5 × 109
4.62 × 108
6.67 × 108
10.35 × 108
Half-life of radium is 1600 yr, then its 1/16th part will remain undecayed after
1200 yr
6400 yr
1800 yr
2200 yr
Atomic number of an atom is Z and mass number is m, then number of neutrons in its nucleus is
m − Z
m + Z
m × Z
A nucleus undergoes β-decay. The mass number and atomic number change as
mass number and atomic number both increases
mass number remain same and atomic number increases
mass number increases and atomic number remain same
mass number and atomic number both decreases
When a radioactive isotope decay in series by the emission of 3 -particles and a β -particle, the isotope finally formed is
The activity of a radioactive element decreases to one third of the original activity I0 , in a period of 9 years. After a further lapse of 9 years, its activity will be
I0
(2/3) I0
I0 / 9
I0 / 6
If Mo is the mass of an oxygen isotope , Mp and Mn are the masses of a proton and a neutron, respectively, the nuclear binding energy of the isotope is
(Mo − 8Mp) c2
(Mo − 8Mp − 9Mn) c2
Moc2
(Mo − 17Mn) c2