Fast neutrons can easily be slowed down by
The use of lead shielding
Passing them through water
Elastic collisions with heavy nuclei
Applying a strong electric field.
Order of magnitude of density of uranium nucleus is, [mp= 1.67x 10-27kg]
1020kg/m3
1017kg/m3
1014kg/m3
1011kg/m3
22Ne nucleus, after absorbing energy, decays into two (-particles and an unknown nucleus. The unknown nucleus is
nitrogen
carbon
boron
oxygen
A nucleus with mass number 220 initially at rest emits an (-particle. If the Q value of the reaction is 5.5 Me V, calculate the kinetic energy of the (-particle
4.4 Me V
5.4 Me V
5.6 Me V
6.5 Me V
During a negative beta decay:
An atomic electron is ejected.
An electron which is already present within the nucleus is ejected.
A neutron in the nucleus decays emitting an electron.
A part of the binding energy of the nucleus is converted into an electron.
During a nuclear fusion reaction:
A heavy nucleus breaks into two fragments by itself.
A light nucleus bombarded by thermal neutrons breaks up
A heavy nucleus bombarded by thermal neutrons break up.
Two light nuclei combine to give a heavier nucleus and possibly other products.
A fresh prepared radioactive source of half life 2hremits radiation of intensity witch is 64 times the permissible safe level. The minimum time after witch it would be possible to work safely with this source is
6 hr
12 hr
24 hr
128 hr
The decay constant of a radioactive sample is (. The half-life and mean-life of the sample are respectively given by:
I/( and (in 2)/(
(In 2) ( and I/(
( (In 2) and I/(
( /(In2) and I/(
A star initially has 1010 deuterons. It produces energy via the processes 1H2 +1H2(1H3 + P, and 1H2 +1H3 (2 He4 +n. If deuteron supply of the star is exhausted in a time of the order of:
106s
108s
1012s
1016s
The half-life period of a radioactive element X is same as the mean-life time of another radioactive element Y. initially both of them have the same number of atoms. Then
X and Y have the same decay rate initially.
X and Y decay at the same rate always
Y will decay at a faster rate than X
X will decay at a faster rate than Y