A certain radioactive element has a half-life of 20 years. If we have a block with 10 g of the element in it, after how many years will there be just 2.5 g of the element in the block?
80 years
40 years
100 years
60 years
The 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
If r1 and r2 are the radii of the atomic nuclei of mass numbers 64 and 125 respectively, then the ratio (r1/r2) is
64/125
5/4
4/5
A radioactive element forms its own isotope after 3 consecutive disintegrations. The particles emitted are
3 β-particles
2 β-particles and 1α-particle
2 -βparticles and 1 γ-particle
2 α-particles and 1 β-particle
A radioactive substance contains 10000 nuclei and its half-life period is 20 days. The number of nuclei present at the end of 10 days is
7070
9000
8000
7500
A radioisotope has a half-life of 5 yr. The fraction of the atoms of this material that would decay in 15 yr will be
1
2/3
7/8
5/8
C.
7/8
Fraction decayed = N0 - N = N0 - (N0/8)
=
A particle of mass m at rest decays into two particles of masses m1 and m2 having non zero velocities. The ratio of de-Broglie wavelengths of the particles is
m1/m2
m2/m1
1.0
In nuclear reaction
the atomic mass and number of P are, respectively:
170,69
172,69
172,70
170,70
A radioactive substance has activity 64 times higher than the required normal level. If T1/2 = 2h, then the time, after which it should be possible to work with it, is:
16 h
6 h
10 h
12 h