The radius of  ₂₉Cu⁶⁴ nucleus in Fermi is (given R₀ = 1.2 × 10^-15 m)

• 9.6

• 4.8

• 1.2

• 7.7

In a radioactive decay, an element _ZX^A emits four α-parti cles, three β-particles and eight gamma photons. The atomic number and mass number of the resulting final nucleus are

• Z − 8, A − 13

• Z − 11, A − 16

• Z − 5, A − 13

• Z − 5, A − 16

A radioactive nucleus has specific binding energy E₁. It emits an α-parti cle. The resulting nucleus has specific binding energy E₂. Then

• E₂ = 0

• E₂ = E₁

• E₂ < E₁

• E₂ > E₁

Pick out the correct statements from the following

1. Electron emission during β-decay is always accompanied by neutrino.
2. Nuclear force is charge independent.
3. Fusion is the chief source of stellar energy.

• I, II are correct

• I, III are correct

• Only I is correct

• II, III are correct

A nucleus ${}_{\mathrm{Z}}{\mathrm{X}}^{\mathrm{A}}$ emits an α-particle with velocity v. The recoil speed of the daughter nucleus is

• $\frac{\mathrm{A} - 4}{4\mathrm{v}}$

• $\frac{4\mathrm{v}}{\mathrm{A} - 4}$

• v

• $\frac{\mathrm{v}}{4}$

A radioactive substance emits 100 beta particles in the first 2 s and 50 beta particles 1n the next 2 s. The mean life of the smaple is

• 4 s

• 2 s

• $\frac{2}{0.693} \mathrm{s}$

• 2 × 0.693 s

Which one of the following is not correct ?

• In forward biased condition diode conducts

• If the packing fraction is negative, the elelment is stable

• B1nd1ng energy is the energy equivalent to mass defect

• Radioactive element can undergo spontaneous fission

108.

A and B are the two radioactive elements. The mixtue of these elements show a total activity of 1200 disintergrations/mmute. The half-life of A is 1 day and that of B is 2 days. What will be the total activity after 4 days? Given, the initial number of atoms in A and B are equal

• 200 dis/min

• 250 dis/min

• 500 dis/min

• 150 dis/min

The binding energy/nucleon of deuteron (₁H²) and the helium atom (₂He⁴) are 1.1 MeV and 7 MeV respectively. If the two deuteron atoms fuse to form a single helium atom, then the energy released is

• 26.9 MeV

• 25.8 MeV

• 23.6 MeV

• 12.9 MeV

The relation between half-life (T) and decay constant (λ) is

• λT = 1

• $\mathrm{\lambda T} = \frac{1}{2}$

• $\mathrm{\lambda T} = {\log }_{\mathrm{e}}2$

• $\mathrm{\lambda } = \log 2\mathrm{T}$