The nuclear reactor at Kaiga is a

• research reactor 

• fusion reactor

• breeder reactor 

• power reactor

A count rate meter shows a count of 240 per minute from a given radioactive source. One hour later the meter shows a count rate of 30 per minute. The half-life of the source is

• 80 min

• 120 min

• 20 min

• 30 min

Two nucleons are at a separation of one Fermi. Protons have a charge of +16 x 10^-19 C. The net nuclear force between them is F₁, if both are neutrons, F₂ if both are protons and F₃ if one is proton and the other is neutron. Then

• F₁ = F₂ > F₃

• F₁ = F₂ = F₃

• F₁ < F₂ < F₃

• F₁ > F₂ > F₃

74.

Mean life of a radioactive sample is 100 seconds. Then its half-life (in minutes) is

• 0.693

• 1

• 10^-4

• 1.155

Consider two nuclei of the same radioactive nuclide. One of the nuclei was created in a supernova explosion 5 billion years ago. The other was created in a nuclear reactor 5 minutes ago. The probability of decay during the next time is

• different for each nuclei

• nuclei created in explosion decays first

• nuclei created in the reactor decays first

• independent of the time of creation

Activity of a radioactive sample decreases to (1/3)^rd of its original value in 3 days. Then,in 9 days its activity will become 

• (1/27) of the original value

• (1/9) of the original value

• (1/18) of the original value

• (1/3) of the original value

If r₁ and r₂ are the radii of the atomic nuclei of mass numbers 64 and 125 respectively, then the ratio (r₁/r₂) is

• $\frac{64}{125}$

• $\sqrt{\frac{64}{125}}$

• $\frac{5}{4}$

• $\frac{4}{5}$

The ionisation energy of Li²⁺ is equal to

• 9hcR

• 6hcR

• 2hcR

• hcR

A radioactive element forms its own isotope after 3 consecutive disintegrations. The particles emitted are

• 3β-particles

• 2β-particles and 1α-particle

• 2β-particles and 1γ-particle

• 2α-particles and 1β-particle

A radioactive substance contains 10000 nuclei and its half-life period is 20 days. The number of nuclei present at the end of 10 days is

• 7070

• 9000

• 8000

• 7500