91.

The phenomena in which proton flips is

• nuclear magnetic resonance

• lasers

• radioactivity

• nuclear fusion

Assume the graph of specific binding energy versus mass number is as shown in the figure. Using this graph, select the correct choice from the following.

• Fusion of two nuclei of mass number lying in the range of 100 < A < 200 will release energy

• Fusion of two nuclei of mass number lying in the range of 51 < A < 100 will release energy

• Fusion of two nuclei of mass number lying in the range of 1 < A < 50 will release energy

• Fission of the nucleus of mass number lying in the range of 100 < A < 200 will release energy when broken into two fragments

Pick out the correct statement from the following.

• Energy released per unit mass of the reactant is less in case of fusion reaction

• Packing fraction may be positive or may be negative

• Pu²³⁹ is not suitable for a fission reaction

• For stable nucleus, the specific binding energy is low

A radioactive sample S₁ having the activity A₁ has twice the number of nuclei as another sample S₂ of activity A₂. If A₁ = 2A₁, then the ratio of half-life of S₂ to the half-life of S₂ is

• 4

• 2

• 0.25

• 0.75

When a neutron is disintegrated to give a β-particle,

• a neutrino alone is emitted

• a proton and neutrino are emitted

• a proton alone is emitted

• a proton and an antineutrino are emitted

The thermonuclear reaction of hydrogen inside the stars is taking place by a cycle of operations. The particular element which acts as a catalyst is

• Nitrogen

• Oxygen

• Helium

• Carbon

The fraction of the initial number of radioactive nuclei which remain undecayed after half of a half-life of the radioactive sample is

• $\frac{1}{4}$

• $\frac{1}{2\sqrt{2}}$

• $\frac{1}{2}$

• $\frac{1}{\sqrt{2}}$

1 curie represents

• 3.7 × 10⁷ disintegrations per second

• 3.7 × 10¹⁰ disintegrations per second

• 10⁶ disintegrations per second

• 1 disintegrations per second

Decay constants of two radio-active samples A and B are 15x and 3x respectively. They have equal number of initial nuclei. The ratio of the number of nuclei left in A and B after a time $\frac{1}{6\mathrm{x}}$ is

• e^-2

• e

• e²

• e^-1

Mass number 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

• in (1), (2) and (3)

• Only in (1)

• in (2), (3)

• in (1), (3)