Nuclei · Question 49

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

If M(A, Z), Mp and Mn denote the masses of the nucleus AZX, proton and neutron respectively in units of u (1 u = 931.5 MeV/c2) and BE represents its binding energy in MeV, then

1. M(A, Z) = ZMp + (A - Z)Mn - BE
2. M(A, Z) = ZMp + (A - Z)Mn + BE/c2
3. M(A, Z) = ZMp + (A - Z)Mn - BE/c2
4. M(A, Z) = ZMp + (A - Z)Mn + BE

If in a nuclear fusion process the masses of the fusing nuclei be m1 and m2 and the mass of the resultant nucleus be m3, then

1. m3 = m1 + m2
2. m3 = |m1 - m2|
3. m3 < (m1 + m2)
4. m3 > (m1 + m2)

A nucleus represented by the symbol AZX has

1. Z neutrons and A - Z protons
2. Z protons and A - Z neutrons
3. Z protons and A neutrons
4. A protons and Z - A neutrons

The half life of radium is about 1600 years. Of 100 g of radium existing now, 25 g will remain unchanged after

1. 4800 years
2. 6400 years
3. 2400 years
4. 3200 years