Nuclei

Two radioactive substances A and B have decay constants 5 and respectively. At t = 0 they have the same number of nuclei. The ratio of number of nuclei of A to those of B will be ( 1e )2 after a time interval

1. 4
2. 2
3. 12
4. 14

In a radioactive decay process, the negatively charged emitted -particles are

1. the electrons produced as a result of the decay of neutrons inside the nucleus
2. the electrons produced as a result of collisions between atoms
3. the electrons orbiting around the nucleus
4. the electrons present inside the nucleus

If the nucleus 2713Al has a nuclear radius of about 3.6 fm, then 12552Te would have its radius approximately as

1. 9.6 fm
2. 12.0 fm
3. 4.8 fm
4. 6.0 fm

The binding energy of deuteron is 2.2 MeV and that of 42He is 28 MeV. If two deuterons are fused to form one 42He then the energy released is

1. 30.2 MeV
2. 25.8 MeV
3. 23.6 MeV
4. 19.2 MeV

In a radioactive material the activity at time t1 is R1 and at a later time t2, it is R2. If the decay constant of the material is , then

1. R1 = R2
2. R1 = R2 e- (t1 - t2)
3. R1 = R2 e (t1 - t2)
4. R1 = R2(t2/t1).

The radius of germanium (Ge) nuclide is measured to be twice the radius of 94Be. The number of nucleons in Ge are

1. 72
2. 73
3. 74
4. 75

In the reaction 21H + 31H 42He + 10n, if the binding energies of 21H, 31H and 42He are respectively a, b and c (in MeV), then the energy (in MeV) released in this reaction is

1. a + b + c
2. a + b - c
3. c - a - b
4. c + a - b

In any fission process the ratio mass of fission productsmass of parent nucleus is

1. equal to 1
2. greater than 1
3. less than 1
4. depends on the mass of the parent nucleus.

Fission of nuclei is possible because the binding energy per nucleon in them

1. increases with mass number at low mass numbers
2. decreases with mass number at low mass numbers
3. increases with mass number at high mass numbers
4. decreases with mass number at high mass numbers.

Which one of the following pairs of nuclei are isotones ?

1. 34Se74, 31Ga71
2. 38Sr84, 38Sr86
3. 42Mo92, 40Zr92
4. 20Ca40, 16S32