Nuclei practice · Mixed difficulty

$\pi$ mesons can be

The half -life period of a radioactive substance is 20 days. What is the time taken for $(7 / 8)^{\text {th }}$ of its original mass to disintegrate?

Our bodies are mostly made of hydrogen $(\mathrm{Z}=1)$, carbon $(Z=6)$, and oxygen $(Z=8)$. In our bodies, are there many more neutrons than protons, many fewer neutrons than protons, or are there about the same number of each?

A radio active material is reduced to $1 / 8$ of its original amount in 3 days. If $8 \times 10^{-3} \, \mathrm{kg}$ of the material is left after 5 days the initial amount of the material is

If the nuclear force between two protons, two neutrons and between proton and neutron is denoted by $\mathrm{F}_{\mathrm{pp}}, \mathrm{F}_{\mathrm{nn}}$ and $\mathrm{F}_{\mathrm{pn}}$ respectively, then

Assertion : Size of nucleus is constant in electron scattering or gamma scattering.

Reason : Electron scattering or gamma scattering is controlled by distribution of charge in
nucleus.

Natural water contains a small amount of tritium $\left({ }_1^3 \mathrm{H}\right)$. This isotope beta-decays with a half-life of 12.5 years. A mountaineer while climbing towards a difficult peak finds debris of some earlier unsuccessful attempt. Among other things he finds a sealed bottle of whisky. On return he analyses the whisky and finds that it contains only 1.5 per cent of the ${ }_1^3 \mathrm{H}$ radioactivity as compared to a recently purchased bottle marked '8 years old'. Estimate the time of that unsuccessful attempt.

${U^{238}}$ decays into $T{h^{234}}$ by the emission of an $\alpha -$ particle. There follows a chain of further radioactive decays, either by $\alpha -$ decay or by $\beta -$ decay. Eventually a stable nuclide is reached and after that, no further radioactive decay is possible. Which of the following stable nuclides is the end product of the ${U^{238}}$ radioactive decay chain

For the stability of any nucleus

During a nuclear fusion reaction

For maintaining sustained chain reaction, the following is required

If a proton and anti-proton come close to each other and annihilate, how much energy will be released

The rate of disintegration of fixed quantity of a radioactive element can be increased by

The phenomenon of pair production is-

Number of neutrons in a gold nucleus with A = 197 and Z = 79 is

Assertion: In He-Ne laser, population inversion takes place between energy level of neon atoms.

Reason: Helium atom has a metastable energy level.

Fusion reactions take place at high temperature because

An accident in a nuclear laboratory resulted in depostion of a certain amount of radioactive material of half - life 18 days inside the laboratory. Tests revealed that the radiation was 64 times more than the permissible level required for safe operation of the laboratory. What is the minimum number of days after which the laboratory can be considered safe for use?

Identify the pair of physical quantities that have same dimensions:

If $50 \%$ of energy released during fission would be converted into electrical energy, then number of fissions in a second in a nuclear reactor of 6.4 $MW$ output is (Energy per fission is $200 \,{MeV}$ )

The half life of a radioactive substance is $\mathrm{T}$. The time taken, for disintegrating $\frac{7}{8}$ th part of its original mass will be:

A radioactive nucleus $A$ finally transforms into a stable nucleus $B$. Then $A$ and $B$ can be

In which radioactive disintegration, neutron dissociates into proton and electron

In the nuclear decay given below:

${ }_{\mathrm{Z}}^{\mathrm{A}} \mathrm{X} \longrightarrow{ }_{\mathrm{Z}+1}^{\mathrm{A}}\mathrm{Y} \longrightarrow{ }_{\mathrm{Z}-1}^{\mathrm{A}-4} \mathrm{~B}^* \longrightarrow{ }_{\mathrm{Z}-1}^{\mathrm{A}-4} \mathrm{~B} \text {, }$

the particles emitted in the sequence are

The decay constant of a radioactive element, which disintegrates to 20 grams from 40 grams in 100 minutes is

Two radioactive substances A and B have decay constant $5\lambda \;$ and $\lambda$ respectively. At t = 0 they have the same number of active nuclei. The ratio of number of active nuclei of A to those of B will be $2\left( {1/{e^2}} \right)$ after a time interval

Assertion: The magnetism of the magnet is due to the spin motion of electron.

Reason: The dipole moment of electron is smaller than that due to orbit motion around nucleus.

A radioactive material has a half life of $\mathrm{10}\,\,\mathrm{days}$. What fraction of the material would remain after $\mathrm{30}\,\,\mathrm{days}$

Calculate no. of fissions of $U^{235}$ required per $\mathrm{sec}$ to generate power of $10 \mathrm{~KW}$.

In a radioactive material the activity at time ${t_1}$ is ${R_1}$ and at a later time ${t_2}$, it is ${R_2}$. If the decay constant of the material is $\lambda$ , then