320 + Interview Questions in NUCLEI IN GENERAL AWARENESS Page 4 InterviewSolution

151.	The principle of controlled chain reaction is used in.A. atomic energy reactorB. atom bomb C. the core of sunD. artificial radioactivity
Answer» Correct Answer - A

Discussion

152.	`overset(10^(21)"per sec")rarr A overset(lambda = 1/30)rarrB`. A shows radioactivity disintegration and it is continuosuly produced at the rate of `10^(21)` per sec. Find maximum number of nuclei of A.
Answer» At maximum `r_"production"=r_"decay"` `10^21=1/30` N `rArr N=30xx10^21`.

Discussion

153.	An archaeologist analyses the wood in a phehistoric structure and finds that `C^14` (Half-life `= 5700` years) to `C^12` only one-fourth of that found in the cells buried plants. The age of the wood is aboutA. 5700 yrB. 2850 yrC. 11400 yrD. 22800 yr
Answer» Correct Answer - C `(N_(0))/(N)=1/4=((1)/(2))^(t//5700)` `therefore" "((1)/(2))^(2)=((1)/(2))^(t//5700)` `therefore" "(t)/(5700)=2` `therefore` The age of the wood, t = 11400 yr

Discussion

154.	A radioactive element A of decay constant `lamda_(A)` decays into another radioactive element B of decay constant `lamda_(B)`. Initially the number of active nuclei of A was `N_(0)` and B was absent in the sample. The maximum number of active nuclei of B is found at t=2. In `2//lamda_(A)`. The maximum number of active nuclei of B isA. `(N_(0))/(4)`B. `(lamda_(A))/(lamda_(B))N_(0)e^(-lamda_(B)t`C. `(lamda_(A))/(lamda_(B)) (N_(0))/(4)`D. None of these
Answer» Correct Answer - C We have, `lamda_(B)N_(B)=lamda_(A)N_(A)` `therefore" "N_(B)=(lamda_(A))/(lamda_(B)).N_(A)` The give time is equivalent to two half-lives of A. Hence, `N_(A)=(N_(0))/(4)" "(thereforeN=N_(0)((1)/(2))^(2)` `N_(B)=(lamda_(A))/(lamda_(B))((N_(0))/(4))`

Discussion

155.	The age of a rock containing lead and uranium is equal to `1.5xx10^9` years. The uranium is decaying into lead with half life equal to `4.5xx10^9` years. Find the ratio of lead to uranium present in the rock, assuming that initially no lead was present in the rock (given `2^(1/3)`=1.259)
Answer» `N_0` is initial amount of uranium . N is present amount of uranium after `1.5xx10^9` years . The amount of lead present is `N_0`-N `therefore` The required ratio is `(N_0-N)/N=(1-e^(-lambdat))/(e^(-lambdat))` Now , `T_(1//2) ="In2"/lambda rArr lambda="ln2"/T_(1//2)` `therefore(N_0-N)/N=(1-e^(-"ln2"^(t/(T//2))))/e^(-"ln2"^(t/(T//2)))=(1-2^(-t/T_(1//2)))/2^(-t/T_(1//2))=(1-2^(-1/3))/(2^(-1/3))=2^(1//3)-1=0.259`

Discussion

156.	A radioactive substance (A) is not produced at a constant rate which decays with a decay constant `lambda` to form stable substance (B).If production of A starts at t=0 . Find (i)The number of nuclei of A and (ii)Number of nuclei at any time t.
Answer» (i)Let N be the number of nuclei of A at any time t `"dN"/"dt"=alpha-lambdaN` `int_0^N"dN"/(alpha-lambdaN)=int_0^t"dt"` On solving , we will get `N=alpha/lambda(1-e^(-lambdat))` (ii) Number of nuclei of B at any time t `N_B=alphat-N_A` `=alphat-alpha/lambda(1-e^(-lambdat))` `=alpha/lambda(lambdat-1+e^(-lambdat))`

Discussion

157.	Carbon dating is best suited for determining the age of fossils of their age in years is of the order ofA. `10^3`B. `10^4`C. `10^5`D. `10^6`
Answer» Correct Answer - b Carbon dating is best suited for determining the age of fossils, if their age is of the order of `10^4` years.

Discussion

158.	What is Q value of nuclear reaction ?
Answer» The Q-value of a nuclear process is Q = final kinetic energy – initial kinetic energy. Due to conservation of mass-energy, this is also, Q = (sum of initial masses – sum of final masses) c²

158.

What is Q value of nuclear reaction ?

Answer»

The Q-value of a nuclear process is

Q = final kinetic energy – initial kinetic energy.

Due to conservation of mass-energy, this is also,

Q = (sum of initial masses – sum of final masses) c²

Discussion

159.	What is nuclear fusion ? Write the conditions for nuclear fusion to occur.
Answer» Nuclear fusion : The process of combining lighter nuclei to produce a large nucleus is known as nuclear fusion. E.g : Hydrogen nuclei `(._(1)H^(1))` are fused together to form heavy Helium `(._(2)He^(4))` along with 25.71 MeV energy released. Conditions for nuclear fusion : 1. Nuclar dusion occurs at very high temperatures such as `10^(7)` kelvin and very high pressures. These are obtained under the explosion of an atom bomb. 2. Higher density is also desirable so that collisions between light nuclei occur quite frequently.

Discussion

160.	What is nuclear fission ? Given an example to illustrate it.
Answer» Nuclear fission : The process of dividing a heavy nucles into two or more smaller and stable nuclei due to nuclear reaction is called nuclear fission. Ex : The fission reaction is `._(92)^(235)U + ._(0)^(1)n to._(56)^(141)Ba+ ._(36)^(92)Kr + 3 ._(0)^(1)n+Q` Where Q is the energy released. Q = (Total mass of reactants - Total mass of product) `C^(2)` `= [("Mass of " ._(92)^(235)U + "Mass of" ._(0)^(1)n) - ("Mass of" ._(56)^(141)Ba + "Mass of" ._(36)^(92)Kr + "Mass of three neutrons")]C^(2)` `= (235.043933 - 140.9177 - 91.895400 - 2xx1.008665) amu xx C^(2)`. `= 0.2135xx931.5 MeV = 198.9 MeV = 200 MeV`

Discussion

161.	In a `n - p - n` transistor circuit, the collector current is `10 mA`. If 95 per cent of the electrons emitted reach the collector, which of the following statements are true ?A. The emitter current will be `8 mA`B. The emitter current will be `10.53 mA`C. The base current will be `0.53 mA`D. The base current will be `2 mA`
Answer» Correct Answer - B::C Here, `I_(0) = 10 mA`, Also, `I_(0) = (95)/(100) I_(e)` `rArr I_(e) = (10 xx 100)/(95) = 10.53 mA` Also, `I_(b) = I_(e) - I_(c) = 10.53 - 10 = 0.53 mA`

Discussion

162.	Mx and My denote the atomic masses of the parent and the daughter nuclei respectively in a radioactive decay. The Q-value for a β – decay is Q1 and that for a β + decay is Q2. If me denotes the mass of an electron, then which of the following statements is correct? (a) Q1 = (Mx – My) c2 and Q2 = (Mx – My – 2me)c2 (b) Q1 = (Mx – My) c2 and Q2 = (Mx – My )c2 (c) Q1 = (Mx – My – 2me) c2 and Q2 = (Mx – My +2 me)c2 (d) Q1 = (Mx – My + 2me) c2 and Q2 = (Mx – My +2 me)c2
Answer» (a) Q₁ = (M_x – M_y) c² and Q₂ = (M_x – M_y – 2m_e)c²

Discussion

163.	The mass number of a nucleus is equal toA. Electrons it containsB. Neutrons it containsC. Protons it containsD. Nucleons it contains
Answer» Correct Answer - D

Discussion

164.	An element `A` decays into element `C` by a two-step process : `A rarr B + ._2 He^4` `B rarr C + 2 e overline` Then.A. A and C are isotopesB. A and C are isobarsC. B and C are isotopesD. A and B are isobars
Answer» Correct Answer - a `._Z^A A to ._(Z-2)^(A-4)B + ._2^4He ` `._(Z-2)^(A-4)B to ._Z^(A-4)C + 2_(-1)^0 e` Hence, A and C are isotopes

Discussion

165.	Outside a nucleus.A. Neutron is unstableB. Proton and neutron both are stableC. Neutron is stableD. Neither neutron nor proton is stable
Answer» Correct Answer - A

Discussion

166.	A nucleus of `Ux_1` has a half life of 24.1 days. How long a sample of `Ux_1` will take to change to 90% of `Ux_1`.A. 80 daysB. 40 daysC. 20 daysD. 10 days
Answer» Correct Answer - a Here, `lambda=0.693/(T_(1//2)) =0.693/24.1=0.02876 "day"^(-1)` `N=N_0-90%` of `N_0 = N_0/10` As N=`N_0e^(-lambdat)` `therefore N_0/10=N_0e^(-lambdat)` or `1/10 = e^(-lambdat)` or `10=e^(lambdat)` or `log_e10= lambdat` `therefore t=1/lambda_"log"_e 10=(2.303 log 10)/0.02870 = (2.303xx1)/0.02876 `= 80 days

Discussion

167.	Outside a nucleus.A. neutron is stableB. proton and neutron both are stableC. neutron is unstableD. neither neutron nor proton is stable
Answer» Correct Answer - c Outside a nucleus, neutron is unstable.

Discussion

168.	Nucleus of an atom whose mass number is 24 consists ofA. 11 electrons ,11 protrons and 13 eutronsB. 11 electrons 13 proton and 1 neutronsC. 11 protons and 3 protonsD. 11 protons and 31 electrons
Answer» Correct Answer - a Nucleus of an atom whose atomic mass is 24 consists of 11 protons and 13 electrons.

Discussion

169.	In helium nucleus, there are.A. 2 proons and 2 elecronsB. 2 neutrons ,12 protons and 2 electronsC. 2 protons and 2 neutronsD. 2 positrons and 2 protons
Answer» Correct Answer - c Helium nucleus `=""_(2)He^(4)`

Discussion

170.	For a nucleus to be stable, the correct relation between neutron number `N` and proton number `Z` is.A. NgtZB. N=ZC. NltZD. Ngtz
Answer» Correct Answer - b For stability in case of lighter nuclei `N/Z=1` and for heavier nuclei `N/Zgt1.`

Discussion

171.	For a nucleus to be stable, the correct relation between neutron number `N` and proton number `Z` is.A. N=ZB. `N ge Z`C. N lt ZD. N gt Z
Answer» Correct Answer - B

Discussion

172.	The force acting between proton and proton inside the nucleus is.A. CoulombB. NuclearC. Neither coulombic or nuclearD. Both coulombic & nuclear
Answer» Correct Answer - D

Discussion

173.	20% of a radioactive substances decay in 10 days . Calculate the amount of the original material left after 30 days.A. `78%`B. `62%`C. `51%`D. `48%`
Answer» Correct Answer - C ( c) amount of element left undecayed after 10 days `=1-(20)/(100)=(8)/(10)` now ,`N =(8)/(10)N_(0) and t= 10` days we have ,`N=N_(0) e^(-lamda t)` `(8)/( 10) N_(0)=N_(0) e^(-lamda t) implies =(10)/(8)implies lamda =(log_(e) (10//8))/(10)` ` therefore lamda = 0.022` if `T_(1//2)` is half -life period ` T_(1//2)=(0.693)/(lamda ) =(0.693)/(0.022)=31.5 `days Again ,` N=N_(0) ((1)/(2))^(n)=N_(0) ((1)/(2))^((31.5)/(30))` `implies % "of" N//N_(0) = 51.2%`

Discussion

174.	State the Radioactivity.
Answer» Radioactivity is the phenomenon in which nuclei of a given species transform by giving out a or b or g rays; a-rays are helium nuclei; b-rays are electrons. g-rays are electromagnetic radiation of wavelengths shorter than X-rays; A. H. Becquerel discovered radioactivity in 1896 purely by accident. Experiments performed subsequently showed that radioactivity was a nuclear phenomenon in which an unstable nucleus undergoes a decay. This is referred to as radioactive decay. Three types of radioactive decay occur in nature : (i) α-decay in which a helium nucleus ⁴₂He is emitted; (ii) β-decay in which electrons or positrons (particles with the same mass as electrons, but with a charge exactly opposite to that of electron) are emitted; (iii) γ-decay in which high energy (hundreds of keV or more) photons are emitted. Each of these decay will be considered in subsequent sub-sections.

174.

State the Radioactivity.

Answer»

Radioactivity is the phenomenon in which nuclei of a given species transform by giving out a or b or g rays; a-rays are helium nuclei; b-rays are electrons. g-rays are electromagnetic radiation of wavelengths shorter than X-rays;

A. H. Becquerel discovered radioactivity in 1896 purely by accident. Experiments performed subsequently showed that radioactivity was a nuclear phenomenon in which an unstable nucleus undergoes a decay. This is referred to as radioactive decay.

Three types of radioactive decay occur in nature :

(i) α-decay in which a helium nucleus ⁴₂He is emitted;

(ii) β-decay in which electrons or positrons (particles with the same mass as electrons, but with a charge exactly opposite to that of electron) are emitted;

(iii) γ-decay in which high energy (hundreds of keV or more) photons are emitted. Each of these decay will be considered in subsequent sub-sections.

Discussion

175.	The variation of decay rate of two radioactive samples A and B with time is shown in Fig. 13.1. Which of the following statements are true? (a) Decay constant of A is greater than that of B, hence A always decays faster than B. (b) Decay constant of B is greater than that of A but its decay rate is always smaller than that of A. (c) Decay constant of A is greater than that of B but it does not always decay faster than B. (d) Decay constant of B is smaller than that of A but still its decay rate becomes equal to that of A at a later instant.
Answer» (c), (d) (c) Decay constant of A is greater than that of B but it does not always decay faster than B. (d) Decay constant of B is smaller than that of A but still its decay rate becomes equal to that of A at a later instant.

175.

The variation of decay rate of two radioactive samples A and B with time is shown in Fig. 13.1. Which of the following statements are true? (a) Decay constant of A is greater than that of B, hence A always decays faster than B. (b) Decay constant of B is greater than that of A but its decay rate is always smaller than that of A. (c) Decay constant of A is greater than that of B but it does not always decay faster than B. (d) Decay constant of B is smaller than that of A but still its decay rate becomes equal to that of A at a later instant.

Answer»

(c), (d)

(c) Decay constant of A is greater than that of B but it does not always decay faster than B.

(d) Decay constant of B is smaller than that of A but still its decay rate becomes equal to that of A at a later instant.

Discussion

176.	He32 and He31 nuclei have the same mass number. Do they have the same binding energy?
Answer» No, the binding energy of H³₁ is greater.

Discussion

177.	In a radioactive substance at `t = 0`, the number of atoms is `8 xx 10^4`. Its half-life period is `3` years. The number of atoms `1 xx 10^4` will remain after interval.A. 6 yearsB. 24 yearsC. 3 yearsD. 9 years
Answer» Correct Answer - D

Discussion

178.	Some radioactive nucleus may emit.A. All the three `alpha,beta` and `gamma` simultaneouslyB. Only `alpha` and `beta` simultaneouslyC. All the three `alpha,beta and gamma` one after anotherD. `gamma` along with `alpha` or `beta` particles
Answer» Correct Answer - D

Discussion

179.	What are thermal neutrons ? What is their importance ?
Answer» Neutrons having kinetic energies approximately 0.025 eV are called as slow neutrons or thermal neutrons. `.^(235)U` undergoes fission only when bombarded with thermal neutrons.

Discussion

180.	A nucleus contains no electrons but can emit them. How ?
Answer» When the nucleus disintegrates and radiates `beta` - rays, it is said to be `beta` - decay. `beta` - particles are nothing but electrons. So the the nucles eject electrons.

Discussion

181.	What are delayed neutrons ?
Answer» Neutrons are emitted in the fission products after sometime are called delayed neutrons.

Discussion

182.	What are the units and dimension of the disintegration contant ?
Answer» `lambda = -(0.693)/(T)` Units `= sec^(-1)` Dimensions = -1

Discussion

183.	Why do all electrons emitted during `beta` - decay not have the same energy ?
Answer» When a neutron is converted into a proton, an electron and neutron are emitted along with it `._(1)^(1)n rarr ._(1)^(1)H + ._(-1)^(0)e +V` In `beta` - decay proten remains in the nucleus, but electron and neutrion are emitted with constant energy. The energy of neutrion is not constant. So, all electrons do not have same energy.

Discussion

184.	Complete the decay reaction `._10Na^(23) to?+._-1e^0+?` Also, find the maximum KE of electrons emitted during this decay. Given mass of `._10Na^(23)=22.994465 u`. mass of `._11Na^(23)=22.989768u`.
Answer» Correct Answer - `._11Na^23` Conservation of charge Conservation of mass number

Discussion

185.	Neutrons cannot produce ionization. Why ?
Answer» Because neutrons are uncharged particles and cannot produce ionization.

Discussion

186.	In the nuclear reaction `._92 U^238 rarr ._z Th^A + ._2He^4`, the values of `A` and `Z` are.A. A=234 , Z=94B. A=238, Z=90C. Z=238, Z=94D. A=234 , Z=90
Answer» Correct Answer - D

Discussion

187.	What is the approximate percentage of mass converted into energy in the following thermonuclear reaction ? `._1H^2+._1H^2+._1H^2 to ._2He^4 + ._1H^1 +._0n^1+21.6` MeV
Answer» Correct Answer - `0.4%` The six nucleons have a total mass of 6 amu, whose energy equivalent is 6 x 931 MeV. Divide energy released by 6 x 931 MeV and multiply by 100.

Discussion

188.	Calculate the maximum energy that a `beta` particle can have in the following decay: `._(8)O^(19) to ._(9)F^(19)+._(-1)e^(0)+barnu` Given, `m(._(8)O^(19))=19.003576u, m(._(9)F^(19))=18.998403u, m(._(-1)e^(0))=0.000549u`
Answer» Correct Answer - 4.3049 MeV Q-value of `beta`-decay =`(m(._8O^19) -{m(._9F^19) + m(._(-1)e^0)}` The energy is shared by `beta^-` particle , if `barv` does not get any share.

Discussion

189.	Neutrons are the best projectiles to produce nuclear reactions. Why ?
Answer» Neutrons are uncharged particles. So they do not deflected by the electric and magnetic fields. Hence Neutrons are considered as best projectiles in nuclear reaction.

Discussion

190.	A star converts all its hydrogen to helium, achieving 100% helium composition. It then converts the helium to carbon via the reaction `._2He^4 + ._2He^4+ ._2He^4 to._6C^(12)+7.27MeV` The mass of the star is `5.0xx10^(32)kg` and it generates energy at the rate of `5xx10^(30)` watt. How long will it take to convert all the helium to carbon at this rate?
Answer» Correct Answer - `1.85xx10^8` year Total number of helium atoms =`(6.023xx10^23)/(4xx10^(-3))xx5.0xx10^32` atoms =`7.52875 xx10^58` atoms 3 helium atoms produce 7.27 MeV of energy =`7.27xx1.6xx10^(-13)`J `"Total energy produced by all the atoms"/"Power"`=Time taken

Discussion

191.	Light energy emitted by star is due toA. breaking of nucleiB. joining of nucleiC. burning of nucleiD. reflection of solar light
Answer» Correct Answer - b Light energy emitted by stars is due to fusion of light nuclei

Discussion

192.	ENERGY CONSERVATION IN NUCLEAR REACTIONA. mass onlyB. energy onlyC. momentum onlyD. mass, energy and momentum
Answer» Correct Answer - d In any nuclear reaction mass , energy and momentum all are conserved.

Discussion

193.	which of the following are used as control rods in a nuclear reacto ?A. cadmiumB. graphiteC. kryptonD. plutonium
Answer» Correct Answer - a In nuclear reactors cadmium rods are used as control rods.

Discussion

194.	Write nuclear reaction equations for Electron capture of `._(54)^(120)Xe`
Answer» `._(54)Xe^(120)+._(-1)e^(0)rarr ._(53)X^(120)`

Discussion

195.

The figure shows the potential energy of a pair of nuclear particles and their distance of separation in Fermi (fm).1. Fill in the blanks.Distance of separationPotential energyNuclear forcer>3 fm r0 <r<3 fmNuclear force is attractiver<r0Potential energy positive2. What conclusion do you obtain about the nature of nuclear force from the graph

Answer»

1.

Distance of separation	Potential energy	Nuclear force
r>3 fm	Potential energy very small and negative	No nuclear force
r₀ <r<3 fm	Potential energy is negative	Nuclear force is attractive
r<r₀	Potential energy positive	Nuclear force is repulsive

2. The nuclear force is a short range force.

Discussion

196.	Obtain the binding energy of a nitrogen nucleus 147N Given m = 147N 14.00307 u.
Answer» Here Z = 7 and A = 14, A – Z = 14 – 7 = 7 ∴ Mass defect = [Z m_H + (A – Z)m_n – M_n] u = (7 × 1.00783 + 7 × 1.00867 – 14.00307) u = (7.05481 + 7.06069 - 14.00307) u = 0.11243 u Since I u = 931.5 MeV ∴ B.E. of 14N = 0.11243 × 931 Mev = 104.7 MeV.

196.

Obtain the binding energy of a nitrogen nucleus 147N Given m = 147N 14.00307 u.

Answer»

Here Z = 7 and A = 14, A – Z = 14 – 7 = 7

∴ Mass defect

= [Z m_H + (A – Z)m_n – M_n] u

= (7 × 1.00783 + 7 × 1.00867 – 14.00307) u

= (7.05481 + 7.06069 - 14.00307) u = 0.11243 u

Since I u = 931.5 MeV

∴ B.E. of 14N = 0.11243 × 931 Mev

= 104.7 MeV.

Discussion

197.	Binding energy curve shows the variation of Binding energy per nucleon of nuclei with mass number.1. Binding energy per nucleon is maximum for mass number…….2. The figure shows dis integration of Deuteron.What should be the frequency of the incident photon to break Deuteron into proton and neutron?Mass of proton mp = 1,007276u.Mass of neutron mn = 1,008665uMass of deuteron = 2.013553u
Answer» 1. 56 2. Mass defect = (1.007276 + 1.008665) – 2.013553 = 0.002388u Binding Energy = 0.002388 × 931 MeV = 2.223 MeV Energy supplied to the photon = 2.223 × 10⁶ × 1.6 × 10^-19 = 3.56 × 10^-13J Frequency of photon v = \(\frac{E}{h}=\frac{3.56\times10^{-13}}{6.62\times10^{34}}\) = 5.4 x 10²⁰Hz

197.

Binding energy curve shows the variation of Binding energy per nucleon of nuclei with mass number.1. Binding energy per nucleon is maximum for mass number…….2. The figure shows dis integration of Deuteron.What should be the frequency of the incident photon to break Deuteron into proton and neutron?Mass of proton mp = 1,007276u.Mass of neutron mn = 1,008665uMass of deuteron = 2.013553u

Answer»

1. 56

2. Mass defect = (1.007276 + 1.008665) – 2.013553 = 0.002388u

Binding Energy = 0.002388 × 931 MeV = 2.223 MeV

Energy supplied to the photon

= 2.223 × 10⁶ × 1.6 × 10^-19

= 3.56 × 10^-13J

Frequency of photon

v = \(\frac{E}{h}=\frac{3.56\times10^{-13}}{6.62\times10^{34}}\) = 5.4 x 10²⁰Hz

Discussion

198.	The binding energy per nucleon is maximum in the case of.A. `""_(2)^(4)He`B. `""_(26)^(56)Fe`C. `""_(56)^(141)Ba`D. `""_(92)^(235)U`
Answer» Correct Answer - B

Discussion

199.	Let `m_p` be the mass of a proton , `m_n` the mass of a neutron, `M_1` the mass of a `._10^20Ne` nucleus and `M_2` the mass of a `._20^40Ca` nucleus . ThenA. `M_2 = M_1`B. `M_2 gt M_1`C. `M_2 lt 2M_1`D. `M_1 lt 10 (m_n + m_p)`
Answer» Correct Answer - d Due to mass defect, the rest mass of a nucleus is always less than sum of the rest masses of its constituent nucleons. `._10^20Ne` nucleus consists of 10 protons and 10 neutrons . `therefore M_1 lt 10 (m_p + m_n)`

Discussion

200.	Average `K.E` of thermal neutron is of the order of (in `KeV`)A. 3 eVB. 0.03 eVC. 3 KeVD. 3 Mev
Answer» Correct Answer - B

Discussion

Explore topic-wise InterviewSolutions in .

The principle of controlled chain reaction is used in.A. atomic energy reactorB. atom bomb C. the core of sunD. artificial radioactivity

`overset(10^(21)"per sec")rarr A overset(lambda = 1/30)rarrB`. A shows radioactivity disintegration and it is continuosuly produced at the rate of `10^(21)` per sec. Find maximum number of nuclei of A.

An archaeologist analyses the wood in a phehistoric structure and finds that `C^14` (Half-life `= 5700` years) to `C^12` only one-fourth of that found in the cells buried plants. The age of the wood is aboutA. 5700 yrB. 2850 yrC. 11400 yrD. 22800 yr

The age of a rock containing lead and uranium is equal to `1.5xx10^9` years. The uranium is decaying into lead with half life equal to `4.5xx10^9` years. Find the ratio of lead to uranium present in the rock, assuming that initially no lead was present in the rock (given `2^(1/3)`=1.259)

A radioactive substance (A) is not produced at a constant rate which decays with a decay constant `lambda` to form stable substance (B).If production of A starts at t=0 . Find (i)The number of nuclei of A and (ii)Number of nuclei at any time t.

Carbon dating is best suited for determining the age of fossils of their age in years is of the order ofA. `10^3`B. `10^4`C. `10^5`D. `10^6`

What is Q value of nuclear reaction ?

What is nuclear fusion ? Write the conditions for nuclear fusion to occur.

What is nuclear fission ? Given an example to illustrate it.

The mass number of a nucleus is equal toA. Electrons it containsB. Neutrons it containsC. Protons it containsD. Nucleons it contains

An element `A` decays into element `C` by a two-step process : `A rarr B + ._2 He^4` `B rarr C + 2 e overline` Then.A. A and C are isotopesB. A and C are isobarsC. B and C are isotopesD. A and B are isobars

Outside a nucleus.A. Neutron is unstableB. Proton and neutron both are stableC. Neutron is stableD. Neither neutron nor proton is stable

A nucleus of `Ux_1` has a half life of 24.1 days. How long a sample of `Ux_1` will take to change to 90% of `Ux_1`.A. 80 daysB. 40 daysC. 20 daysD. 10 days

Outside a nucleus.A. neutron is stableB. proton and neutron both are stableC. neutron is unstableD. neither neutron nor proton is stable

Nucleus of an atom whose mass number is 24 consists ofA. 11 electrons ,11 protrons and 13 eutronsB. 11 electrons 13 proton and 1 neutronsC. 11 protons and 3 protonsD. 11 protons and 31 electrons

In helium nucleus, there are.A. 2 proons and 2 elecronsB. 2 neutrons ,12 protons and 2 electronsC. 2 protons and 2 neutronsD. 2 positrons and 2 protons

For a nucleus to be stable, the correct relation between neutron number `N` and proton number `Z` is.A. NgtZB. N=ZC. NltZD. Ngtz

For a nucleus to be stable, the correct relation between neutron number `N` and proton number `Z` is.A. N=ZB. `N ge Z`C. N lt ZD. N gt Z

The force acting between proton and proton inside the nucleus is.A. CoulombB. NuclearC. Neither coulombic or nuclearD. Both coulombic & nuclear

20% of a radioactive substances decay in 10 days . Calculate the amount of the original material left after 30 days.A. `78%`B. `62%`C. `51%`D. `48%`

State the Radioactivity.

He32 and He31 nuclei have the same mass number. Do they have the same binding energy?

In a radioactive substance at `t = 0`, the number of atoms is `8 xx 10^4`. Its half-life period is `3` years. The number of atoms `1 xx 10^4` will remain after interval.A. 6 yearsB. 24 yearsC. 3 yearsD. 9 years

Some radioactive nucleus may emit.A. All the three `alpha,beta` and `gamma` simultaneouslyB. Only `alpha` and `beta` simultaneouslyC. All the three `alpha,beta and gamma` one after anotherD. `gamma` along with `alpha` or `beta` particles

What are thermal neutrons ? What is their importance ?

A nucleus contains no electrons but can emit them. How ?

What are delayed neutrons ?

What are the units and dimension of the disintegration contant ?

Why do all electrons emitted during `beta` - decay not have the same energy ?

Complete the decay reaction `._10Na^(23) to?+._-1e^0+?` Also, find the maximum KE of electrons emitted during this decay. Given mass of `._10Na^(23)=22.994465 u`. mass of `._11Na^(23)=22.989768u`.

Neutrons cannot produce ionization. Why ?

In the nuclear reaction `._92 U^238 rarr ._z Th^A + ._2He^4`, the values of `A` and `Z` are.A. A=234 , Z=94B. A=238, Z=90C. Z=238, Z=94D. A=234 , Z=90

What is the approximate percentage of mass converted into energy in the following thermonuclear reaction ? `._1H^2+._1H^2+._1H^2 to ._2He^4 + ._1H^1 +._0n^1+21.6` MeV

Calculate the maximum energy that a `beta` particle can have in the following decay: `._(8)O^(19) to ._(9)F^(19)+._(-1)e^(0)+barnu` Given, `m(._(8)O^(19))=19.003576u, m(._(9)F^(19))=18.998403u, m(._(-1)e^(0))=0.000549u`

Neutrons are the best projectiles to produce nuclear reactions. Why ?

Light energy emitted by star is due toA. breaking of nucleiB. joining of nucleiC. burning of nucleiD. reflection of solar light

ENERGY CONSERVATION IN NUCLEAR REACTIONA. mass onlyB. energy onlyC. momentum onlyD. mass, energy and momentum

which of the following are used as control rods in a nuclear reacto ?A. cadmiumB. graphiteC. kryptonD. plutonium

Write nuclear reaction equations for Electron capture of `._(54)^(120)Xe`

Obtain the binding energy of a nitrogen nucleus 147N Given m = 147N 14.00307 u.

The binding energy per nucleon is maximum in the case of.A. `""_(2)^(4)He`B. `""_(26)^(56)Fe`C. `""_(56)^(141)Ba`D. `""_(92)^(235)U`

Let `m_p` be the mass of a proton , `m_n` the mass of a neutron, `M_1` the mass of a `._10^20Ne` nucleus and `M_2` the mass of a `._20^40Ca` nucleus . ThenA. `M_2 = M_1`B. `M_2 gt M_1`C. `M_2 lt 2M_1`D. `M_1 lt 10 (m_n + m_p)`

Average `K.E` of thermal neutron is of the order of (in `KeV`)A. 3 eVB. 0.03 eVC. 3 KeVD. 3 Mev