CBSE
Multiple Choice QuestionsWhich one of the following is used as a moderator in nuclear reaction?
Uranium
Heavy water
Cadmium
Plutonium
In a radioactive decay,
92U238 X ZYA
The values of Z and A
92 , 236
88 , 230
90 , 130
88 , 234
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
Number of nuclei of a radioactive substance at time t = O are 2000 and 1800 at time t = 2s. Number of nuclei left after t = 6s is
1442
1554
1652
1458
In a sample of radioactive substance, what percentage decays in one mean life time?
69.3 %
63 %
50 %
36 %
A radioactive substance containing N atoms emits n - particles per second. Half-life of the substance is :
sec
sec
sec
sec
The radius of nucleus of silver (atomic number = 47) is 3.4 x 10-14 m. The electric potential on the surface of nucleus is (e = 1.6 x 10-19 C)
1.99 x 106 V
2.9 x 106 V
4.99 × 106 V
0.99 x 106 V
Half-life of radium is 1600 yr, then its 1/16th part will remain undecayed after
1200 yr
6400 yr
1800 yr
2200 yr
92U238 on absorbing a neutron goes over to 92U239. This nucleus emits an electron to go over to neptunium which on further emitting an electron goes over to plutonium. The resulting plutonium can be expressed as
94Pu239
90Pu219
93Pu240
92Pu240
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
