Mass numbers of the elements A, B, C and D are 30, 60, 90 and 120 respectively. The specific binding energy of them are 5 MeV, 8.5 MeV, 8 MeV and 7 MeV respectively. Then, in which of the following reaction/s energy is released
(1) D 2B (2) C B + A
(3) B 2A
1. Only in (1)
2. In (2), (3)
3. In (1), (3)
4. In (1), (2) and (3)
The binding energy per nucleon of is 7.97 MeV and that of is 7.75 MeV. The energy (in MeV) required to remove a neutron from is
1. 3.52
2. 3.64
3. 4.23
4. 7.86
Two radioactive materials have decay constants and respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei to that of will be 1/e after a time
1.
2.
3.
4.
The activity of a radioactive sample is measured as counts per minute at t = 0 and /e counts per minute at t = 5 minutes. The time (in minutes) at which the activity reduces to half its value is
1. 5 log2
2. log 2/5
3.
4. 5 2
Half-life of a radioactive substance is 20 minutes. Difference between points of time when it is 33% disintegrated and 67% disintegrated is approximately -
1. 10 min
2. 20 min
3. 30 min
4. 40 min
The rest mass of an electron as well as that of positron is 0.51 MeV. When an electron and positron are annihilated, they produce gamma-rays of wavelength (s)
1. 0.012
2. 0.024
3. 0.012
4. 0.024
In the nuclear fusion reaction , given that the repulsive potential energy between the two nuclei is -7.7 x 10 J, the temperature at which the gases must be heated to initate the reaction is nearly -
[Boltzmann's constant k = 1.38 x 10 J/K]
1. K
2. K
3. K
4. K
A nucleus with mass number 220 initially at rest emits an -particle. If the Q value of the reaction is 5.5 MeV, calculate the kinetic energy of the -particle
1. 4.4 MeV
2. 5.4 MeV
3. 5.6 MeV
4. 6.5 MeV
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
1. X and Y have the same decay rate initially
2. X and Y decay at the same rate always
3. Y will decay at a faster rate than X
4. X will decay at a faster rate than Y
A radioactive material decays by simultaneous emission of two particles with respective half lives 1620 and 810 years. The time (in years) after which one - fourth of the material remains is
1. 1080
2. 2430
3. 3240
4. 4860
A radioactive sample having an activity of 5Ci has twice the number of nuclei as another sample which has an activity of 10Ci. The half lives of and can be
1. 20 years and 5 years, respectively
2. 20 years and 10 years, respectively
3. 10 years each
4. 5 years each
A radioactive sample consists of two distinct species having equal number of atoms initially. The mean life time of one species is and that of the other is 5 . The decay products in both cases are stable. A plot is made of the total number of radioactive nuclei as a function of time. Which of the following figures best represents the form of this plot ?
1.
2.
3.
4.
Radioactive elements decays to form a stable nuclide, then the rate of decay of reactant will vary with time (t) as shown in figure
1.
2.
3.
4.