Nuclei practice · Medium

$\mathrm{1}$ curie represents

Assertion: Mass defect in nuclear reactions is less than $1 \%$.

Reason: In nuclear reaction, change in BE/N is generally less than $1\%$.

Radioactive decay will occur as follows

$\begin{aligned} & { }_{86}^{22} {Rn} \rightarrow{ }_{84}^{216} {PO}+{ }_2^5 {He} \text { half life }=55 {~s} \\ & { }_{84}^{216} {Po} \rightarrow{ }^{212} {~Pb}+{ }_2^4 {He} \text { half life }=0.66 {~s} \\ & { }_{82}^{82} {~Pb} \rightarrow{ }_{82}^{212} {BL}+\lambda^{\circ} e \text { Half life }=10.6 {~h} \end{aligned}$

If a certain mass of radon $({Rn}=220)$ is allowed to decay in a certain container; then after 5 minutes the element with the greater mass will be

For a nuclear reactor to run in critical condition the reproduction factor ${k}$ should be

The radioactivity of a certain material drops to $\frac{1}{{16}}$ of the initial value in $\mathrm{2}\,\,\mathrm{h}$. The half-life of this radio nuclide is

The $Q - {\text{value}}$ of a nuclear reaction and kinetic energy of the projectile particle, ${K_p}$ are related as:

Sun maintains its shining because of the

In a sample of radioactive material, what percentage of the initial number of active nuclei will decay during one mean life

In a radioactive reaction ^ ₉₂X²³² → ₈₂X²⁰⁴${^\,_{92}}{X^{232}}{ \to _{82}}{X^{204}}$
the number of $\mathrm{\alpha }$-particles emitted is

In a material medium, when a positron meets an electron both the particles annihilate leading to the emission of two gamma ray photons. This process forms the basis of an important diagnostic procedure called

Statement-I: Heavy water absorbs neutrons more efficiently than normal water.

Statement-II: Heavy water has more molecular mass than normal water.

Statement-I: In reactors, light nuclei called modertors are provided along with the fissionable nuclei for slowing down fast neutrons.

Statement-II: In an elastic collision with hydrogen the neutron almost comes to rest and proton carries away the energy.

A radioactive substance has an average life of $\mathrm{5}\,\mathrm{h}$. In a time of $\mathrm{5}\,\mathrm{hours}$

A radioactive substance of half-life 6 min is placed near a Geiger counter which is found to resister $\mathrm{1024}$ particles per minute. How many particles per minute will it register after $\mathrm{42}\,\mathrm{ min}$ ?

If the binding energy per nucleon of deutron is $1.115\,\,\mathrm{MeV}$, its mass defect in atomic mass unit is

If $M(A ; Z), M_p$ and $M_n$ denote the masses of the nucleus ${ }_{\mathrm{Z}}^{\mathrm{A}} \mathrm{X}$, proton and neutron respectively in units of $\mathrm{u}(1 \mathrm{u}=$ $931.5 \mathrm{~MeV} / \mathrm{c}^2$ ) and $\mathrm{BE}$ represents its bonding energy in $\mathrm{~MeV}$, then

Assertion: For nuclear reactor, it is desirable to have $K=1$.

Reason: Sustained chain reaction occur at this critical condition.

During the $\mathrm{\beta } - \mathrm{decay}$

Pick out the correct statement from the following.

The mass of $\alpha$-particle is

Uranium -238 decays to Thorium -234 with half-life $5 \times 10^9 \mathrm{yr}$. The resulting nucleus is in the excited state and hence further emits $\gamma$-rays to come to the ground state. It emits $20 \gamma$-rays per second. The emission rate will drop to $5 \gamma$-rays per second in

$\alpha -$ particle consists of:

The radioactive decay of uranium into thorium is expressed by the equation $_{92}^{238}U \to _{90}^{234}Th\,\, + \,X$, where $'X'$ is

The operation of a nuclear reactor is said to be critical, if the multiplication factor $\left( k \right)$ has a value

Tritium is an isotope of hydrogen whose nucleus triton contains 2 neutrons and 1 proton. Free neutrons decay into $p+e^{-}+\bar{v}$. If one of the neutrons in triton decays, it would transform into ${He}^3$ nucleus. This does not happen. This is because

A nuclear bomb exploded $200\,\,km$ above the surface of moon. The sound of explosion on the moon

A nucleus is bombarded with a high speed neutron so that resulting nucleus is a radioactive one. This phenomenon is called

A nucleus of uranium decays at rest into nuclei of thorium and helium. Then:

When a radioactive substance emits an $\alpha$-particle, its position in the periodic table is lowered by

In ${\mathrm{\beta }^ + }$ decay process, the following changes take place inside the nucleus