CBSE
Multiple Choice QuestionsHalf-lives of two radioactive substances A and B are respectively 20 min and 40 min. Initially the samples of A and B have equal number of nuclei. After 80 min the ratio of remaining number of A and B nuclei is
1 : 16
4 : 1
1 : 4
1 : 1
Hydrogen bomb is based upon
fission
fusion
chemical reaction
transmutation
If r1 and r2 are the radii of the atomic nuclei of mass numbers 64 and 125 respectively, then the ratio ( r1/ r2 ) is
If 82U238 emits 8 - particles and 6 β - particles, then the resulting nucleus is
82U206
82Pb206
82U210
82U214
The half-life of a radio-isotope is 4h. If initial mass of the isotope was 200 g, then mass remaining after 24 h will be
1.042 g
2.084 g
3.125 g
4.167 g
the ionization energy of Li2+ is equal to
9hcR
6hcR
2hcR
hcR
The operation of a nuclear reactor is said to be critical, if the multiplication factor (k) has a value
1
1.5
2.1
2.5
The specific charge of a proton is 9.6 x 107 C/kg. The specific charge of an alpha particle will be
9.6 x107 C/kg
19.2 x 107 C/kg
4.8 x107 C/kg
2.4 x 107 C/kg
If Mo is the mass of an oxygen isotope 8O17 , MP and Mn are the masses of a proton and a neutron, respectively, the nuclear binding energy of the isotope is
( Mo - 8 MP ) c2
( Mo - 8 MP - 9 Mc ) c2
Mo C2
(Mo - 17 Mn ) c2
Activity of a radioactive sample decreases to (1/3)rd of its original value in 3 days. Then, in 9 days its activity will become
(1/27) of the original value
(1/9) of the original value
(1/18) of the original value
(1/3) of the original value
