Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes, respectively. Initially, the samples have equal number of nuclei. After 80 minutes, the ratio of decayed numbers of A and B nuclei will be:
1: 16
4 : 1
1: 4
1: 4
Proton, Deuteron and alpha particle of the same kinetic energy is moving in circular trajectories in a constant magnetic field. The radii of the proton, deuteron and alpha particle are respectively r_{p}, r_{d} and r_{α}. Which one of the following relations is correct?
r_{α} = r_{p}= r_{d}
r_{α} = r_{p}< r_{d}
r_{α} > r_{d}> r_{p}
r_{α} > r_{d}> r_{p}
Assume that a neutron breaks into a proton and an electron. The energy released during this process is(Mass of neutron = 1.6725 x 10^{–27}kg; mass of proton = 1.6725 x 10^{–27}kg; mass of electron = 9 x 10^{–31}kg)
0.73 MeV
7.10 MeV
6.30 MeV
6.30 MeV
The half life of a radioactive substance is 20 minutes. The approximate time interval (t_{2} - t_{1}) between the time t_{2} when 2/3 of it has decayed and time t_{1} when 1/3 of it had decayed is
14 min
20 min
28 min
28 min
A nucleus of mass M + Δm is at rest and decays into two daughter nuclei of equal mass M/2 each. The speed of light is c.
The binding energy per nucleon for the parent nucleus is E_{1} and that for the daughter nuclei is E_{2}. Then
E_{1} = 2E_{2}
E_{2} = 2E_{1}
E_{1} > E_{2}
E_{1} > E_{2}
A nucleus of mass M + Δm is at rest and decays into two daughter nuclei of equal mass M/2 each. Speed of light is c.
The speed of daughter nuclei is
A radioactive nucleus (initial mass number A and atomic number Z) emits 3 α–particles and 2 positions. The ratio of number of neutrons to that of protons in the final nucleus will be
A radioactive nucleus A with a half-life T, decays into a nucleus B. At t = 0, there is no nucleus B. At some time t, the ratio of the number of B to that of A is 0.3. Then, t is given by
t = T log (1.3)
The above is a plot of binding energy per nucleon Eb, against the nuclear mass M; A, B, C, D, E, F correspond to different nuclei. Consider four reactions:
(i) A + B → C + ε (ii) C → A + B + ε
(iii) D + E → F + ε and (iv) F → D + E +ε
where ε is the energy released? In which reaction is ε positive?
(i) and (iv)
(i) and (iii)
(ii) and (iv)
(ii) and (iv)
The transition from the state n = 4 to n = 3 in a hydrogen-like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from
2 → 1
3 → 2
4 → 2
4 → 2