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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 401. |
The percentage of quantity of a radioactive material that remains after 5 half-lives will be .A. `31%`B. `3.125%`C. `0.3%`D. `1%` |
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Answer» Correct Answer - b `(N)/(N_(0))=(1)/(2^(5T//T))` `(N)/(N_(0)) =(1)/(2^(5))` `:. (N)/(N_(0)) xx 100=(100)/(32)=3.125`. |
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| 402. |
The nuclei of which one of the following pairs of nuclei are isotons ?A. `._(34)Se^(74), ._(31)Ga^(71)`B. `._(42)MO^(92), ._(40)Ze^(92)`C. `._(38)Sr^(86), ._(38)Sr^(86)`D. `._(20)Ca^(40), ._(16)S^(32)` |
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Answer» Correct Answer - A |
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| 403. |
Fission of nuclei is possible because the binding energy per nuclei in themA. increases with mass number at high mass numbersB. decreases with mass number at low mass numbersC. increases with mass number at low mass numbersD. decreases with mass number at low mass numbers |
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Answer» Correct Answer - B |
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| 404. |
Fission of nuclei is possible because the binding energy per nuclei in themA. increases with mass number at high mass numbersB. decreases with mass number at high mass numbersC. increases with mass number at low mass numbersD. decreases with mass number at low mass numbers |
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Answer» Correct Answer - B |
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| 405. |
In moon rock sample the ratio of the number of stable argon-`40` atoms present to the number of radioactive potassium`-40` atoms is `7:1`. Assume that all the argon atoms were produced by the decay of potassium atoms, with a half-life of `2.5xx10^(9)yr`. The age of the rock isA. `2.5xx10^(9)yr`B. `5.0xx10^(9) yr`C. `7.5xx10^(9)yr`D. `10^(10)yr` |
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Answer» Correct Answer - C Let the number of radioactive Potassium atoms present initially `(t=0)` is `N_(0)` and the number of stable argon atoms at `t=0` is zero. After time `t` the number stable argon atoms is `m` and the radioactive potassium is `N_(0)-m` gives that `(n_(0)-M)/(m)=(1)/(7), M=(7)/(8)N_(0)-m=(1)/(8)N_(0)` Since after one half-life `N_(0)` reduces to `N_(0)//2` after `2` half-lives `N_(0)//4` and after `3` half-lives it reduces to `N_(0)//8` `t= nT=3xx2.5xx10^(9)` years Thus, `=7.5xx10^(9)` year |
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| 406. |
The half-life of a radioactive sample is `T`. If the activities of the sample at time `t_(1)` and `t_(2)` `(t_(1) lt t_(2))` and `R_(1)` and `R_(2)` respectively, then the number of atoms disintergrated in time `t_(2)-t_(1)` is proportional toA. `(R_(1)-R_(2))T`B. `(R_(1)+R_(2))T`C. `(R_(1)R_(2))/(R_(1)+R_(2))T`D. `(R_(1)R_(2))/(T)` |
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Answer» Correct Answer - A Activity `R= lambda N` so that `R_(1)=lambda N_(1)` and `R_(2)=lambda N_(2)` `R_(1)-R_(2)=lambda(N_(1)-N_(2))=(0.6931)/(T)(N_(1)-N_(2))` `N_(1)-N_(2)=((R_(1)-R_(2))T)/(0.6931)` `N_(1)-N_(2) prop (R_(1)-R_(2))T, :. t_(2)-t_(1) alpha(R_(1)-R_(2))T` |
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| 407. |
Consider the `beta^(-)` decay of `._(12)^(27)Mg` `._(12)^(27)Mgrarr._(13)^(27)Al^(*)+._(-1)^(0)e+vecv` The atomic masses of `Mg^(27)` and `Al^(27)` are 26.98434u and 26.98154u respectively. Mass of electron is 0.00055u. The `Al^(+)` nucleus has excitively. Mass of electron is 1.015MeV. (a) Find the Q value of the `beta^(-)` decay. (b) What is maximum possible kinetic energy of emitted `beta^(-)` particle? (c) Find the smallest wavelenght photon that `Al^(+)` can emit when it de-excites. (d) As an alternative to gamma decay, the excited `Al^(+)` nucleus returns to its ground state by giving up its excitation energy to an atomic electron which has a binding energy of 2300eV. The process is known as internal conservation. Find the kinetic energy of the emitted electron. |
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Answer» Correct Answer - (a) 2.0925MeV (b) `KE_(betalt1.0775MeV` (c) 0.0122 `overset(@)A` (d) 1.013 MeV |
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| 408. |
Following reactions are known as inverse beta decay `p+vecvrarrn+e^(+)` `n+vrarrp+e^(-)` These reactions have extremely low probabilities. Because of this, neutrinos and antineutrinos are able to pass through vast amount of matter without any interaction. In an experiment to detect neutrinos, large number of neutrinos coming out from beta decays of a radioactive material were made to pass through a tank of water, containing a cadmium compound in solution, which provided the protons to interact with antineutrinos, which provided the protons to interact with antineutrinos. Immediately after a proton absorbed a neutrino to yield a positron and a neutron, the positron encountered an electron and both got annihilated. the gamma ray detectors surrounding the tanks responded to the resulting photons. This confirmed that the above reaction has taken place. (a) How many gamma ray photons are produced when a electron annihilates with a positron? What is energy of each photon? Take the mass of an electron to be 0.00055 u. (b) The neutron produced in the above reaction was captured by `.^(112)Cd` to form `.^(113)Cd`. The atomic masses of these two isotopes of cadmium are are 111.9028u and 112.9044u respectively. mass of a neutron is 1.0087u. find the Q value of this reaction. Assume half of this energy is excitation energ of `.^(113)Cd`. if the nucleus de-excites by emitting a gamma ray photon find its wavelenght. |
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Answer» Correct Answer - (a) 0.51MeV (b) 6.60MeV,0.004 `overset(@)A` |
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| 409. |
The half lives of two longest-lived radioactive isotopes of phosphorus `P^(32)` and `P^(33)`, are 14 days and 28 days respectively. A sample has been prepared by mxing the two isotopes in the ratio of 4:1 of their atoms. Initial activity of the mixed sample is 9.0mCi. Find the activity of the sample after 80 days. Take `ln2=0.7` and `e^(-2)=0.14` |
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Answer» Correct Answer - 0.3mCi |
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| 410. |
`A._(7)^(14)N` nucleus, when bombarded by `._(2)^(4)He`, converts into `._(8)^(17)O` accoring to the following reaction. `._(7)^(14)N+._(2)^(4)Herarr._(8)^(17)O+._(1)^(1)H` Atomic masses are: `.^(14)N:14.003u,.^(4)He:4.003u,.^(17)O:16.999u,.^(1)H:1.008u` (a) Find the Q value of the reactions (b) Assume that a `.^(4)He` nucleus collides with a free `.^(14)N` nucleus originally at rest. Calculate the minimum kinetic energy `(k_(0))` that `.^(4)He` must have so as to cause this reaction. (c) If the `.^(17)O` nucleus has an excitation energy of 1.0 MeV, find the minimum kinetic energy `(k_(0))` that `.^(4)He` must have. [Take `1u=930MeV//c^(2)`] |
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Answer» Correct Answer - (a) 0.93MeV (b) `k_(0)=1.20MeV` (c) `k_(0)=2.20MeV` |
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| 411. |
In compound `X(n, alpha) rarr ._(3)Li^(7)`, the element `X` isA. `._(2)He^(4)`B. `._(5)B^(10)`C. `._(5)B^(9)`D. `._(4)Be^(11)` |
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Answer» Correct Answer - B |
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| 412. |
Half-life of a radioactive substance is `12.5 h` and its mass is `256 g`. After what time the amount of remaining substance is `1g`?A. `75 h`B. `100 h`C. `125 h`D. `150 h` |
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Answer» Correct Answer - B |
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| 413. |
In nuclear fission process , energy is released becauseA. mass of products is more than mass of nucleusB. total binding energy of products formed due to nuclear fission is more than the parent fissionable materialC. Total binding energy of products formed due to nuclear fission is less than parent fissionable materialD. mass of some particles is converted into energy |
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Answer» Correct Answer - B |
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| 414. |
Half-life period of a radioactive substance is `6 h`. After `24 h` activity is `0.01 muC`, what was the initial activity ?A. `0.04 muC`B. `0.08 muC`C. `0.24 muC`D. `0.16 muC` |
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Answer» Correct Answer - D |
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| 415. |
In the following nuclear reaction `._(13)Al^(27)+._(2)He^(4)rarr._(15)P^(30)+X,X` will beA. ProtonB. ElectronC. NeutronD. `alpha`-particle |
| Answer» Correct Answer - C | |
| 416. |
If a nucleus emits a gamma-ray, its atomic and mass number _____but there will be ______in the energy of the nucleus. Select suitable pairA. Remain same, increaseB. Remain same,decreaseC. Decrease, increaseD. increase, decrease |
| Answer» Correct Answer - B | |
| 417. |
In `beta-`decay, all the emitted electron do not have the same energy the same energy. `beta-`decay is not a two body decay process.A. If both assertion and reason are true and reason is the correct explanation of assertion.B. If both assertion and reason are true but reason is not the correct explanation of assertion.C. If assertion is true but reason is falseD. If assertion is false but reason is true. |
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Answer» Correct Answer - A (a) Since had it been a two body decay process (like `alpha-`decay), the momentum and energy considerations fix the energy of the emitted particles. |
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| 418. |
The graph which represents the correct variation of logarithm of activity (log A) versus time, in figure is. .A. AB. BC. CD. D |
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Answer» Correct Answer - D (d) Activity `A = lamda N_0 e^(-lamda t)` `rArr log_e A = log_e lamda N_0 + log_e e^(-lamda t)` `rArr log_e A = log_e C - lamda t (Take lamda N_0 = C)` `rArr log_e A = -lamda t + log_e C` This is the equation of a straight line having negative slope `(= -lamda)` and positive intercept in `log_e A` axis. |
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| 419. |
The graph between log `R` and log `A` wher `R` is the nuclear radius and `A` is the mass of is.A. B. C. D. |
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Answer» Correct Answer - A (a) `R = R_0 A^(1//3)` , where `R_0 = 1.2 xx 10^-15 m`. `rArr log_e R = log_e R_0 + (1)/(3) log_e A` This is the equation of a straight line with positive slope. |
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| 420. |
The charge density in a nucleus varies with distance from the centre of the nucleus according to the curve in Fig.A. B. C. D. |
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Answer» Correct Answer - C ( c) Charge density is uniform inside and then falls rapidly near the surface of the nucleus. |
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| 421. |
The half-life of a radioactive substance is `30` minutes, The time (in minutes) taken between `40 %` decay and `85 %` decay of the same radioactive substance is.A. 45B. 60C. 15D. 30 |
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Answer» Correct Answer - B (b) Decay `40 % rarr 85 %` Remaining `60 % rarr 15 %` `60 % overset (t ^1//_2)rarr 30% overset (t ^1//_2)rarr 15 %` `:. t = 2 t_(1//2) = 60 min`. |
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| 422. |
The half-life of a radioactive substance is `30` minutes, The time (in minutes) taken between `40 %` decay and `85 %` decay of the same radioactive substance is.A. `15`B. `30`C. `45`D. `60` |
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Answer» Correct Answer - D |
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| 423. |
Energy is released in nuclear fission. Total binding energy of the fission fragments is large than the total binding energy of the parent nucleus.A. If both assertion and reason are true and reason is the correct explanation of assertion.B. If both assertion and reason are true but reason is not the correct explanation of assertion.C. If assertion is true but reason is falseD. If assertion is false but reason is true. |
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Answer» Correct Answer - A (a) When atoms of an element are bombarded by neutrons, the atomic nuclei are disintegrated and emit lighter particles. This process is called nuclear fission. The mass of the nuclei obtained by fission is less than the mass of the disintegrated nucleus and lost mass reappears in the form of heat according to Einsteinmass energy relation. The total binding energy of the fission fragments is larger than the total binding energy of the parent nucleus, because fission occurs when total mass energy decreases that is `Delta E_(bn)` will decrease. |
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| 424. |
Mass defect of an atom refers toA. inaccurate measurement of mass of nucleonsB. mass annihiliated to produce enegry to bind the nucleusC. packing fractionD. difference in the number of neutrons and protons in the nucleus |
| Answer» Correct Answer - B | |
| 425. |
All nuclei consist of two types of particles- protaon and neutrons. Nuclear force is the strongest froce. Stability of nucleus is determined by the neutron - proton ratio or mass defect or binding energy per nucleus or packing fraction. Shape of nucleus is calculated by quadrupole moment. Spin of nucleus depends on even or odd mass number. Volume of nucleus depends on the mass number. Whole mass of the atom (nearly `99 %`) is centered at the nucleus. Magnetic moment of the nucleus is measured in terms of the nuclear magnetons. The correct statements about nuclear force is/areA. Charge independentB. short-range forceC. non-conservation forceD. spin-dependent force |
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Answer» Correct Answer - a,b,c,d All options are basic properties of nuclear forces. So, all options are correct. |
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| 426. |
Mass defect of an atom refers toA. inaccurate measurment of mass of neutronsB. mass annihilated to produce energy to bind the nucleousC. packing fractionD. difference in the number of neutrons and protons in the nucleus |
| Answer» Correct Answer - B | |
| 427. |
The stability of a nucleus can be measured byA. Average binding energyB. Packing fractionC. Ratio of number of neutrons and protonsD. All the above. |
| Answer» Correct Answer - D | |
| 428. |
Consider the following statements `A` and `B`. Identify for correct in the given answer. A) `p-n , p-p, n-n` forces between nucleons are not equal and charge dependent. B) In nuclear reactor the fission reaction will be in accelerating state if the value of neutron reproduction factor `K gt 1`A. Both `A` and `B` are correctB. Both `A` and `B` are wrongC. `A` is wrong `B` is correctD. `A` is correct `B` is wrong |
| Answer» Correct Answer - C | |
| 429. |
sion giving 0.1 % of its original mass released as energy. (a) How much energy is released by an atomic bomb that contains `10 kg` of `.^(235)U`. (b) If 1 ton TNT releases `4 xx 10^(9)` joule. What is the TNT equivalent of the bomb ? |
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Answer» Correct Answer - `[9 xx 10^(14), 2.25 xx 10^(5) "ton"]` |
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| 430. |
The process of fission is responsible for the release of energy inA. The hydrogen bombB. The atom bombC. The sunD. The star |
| Answer» Correct Answer - B | |
| 431. |
`U-235` can decay by many ways , let us here consider only two ways, `A` and `B`. In decay of `U-235` by means of `A`, the energy released per fission is `210 MeV` while in `B` it is `186 MeV`. Then , the uranium `235` sample is more likely to decay by .A. scheme `A`B. scheme `B`C. equally likely for both schemesD. it depends on half-life of schemes A and `B` |
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Answer» Correct Answer - a Since scheme A release more energy than scheme B, scheme A is more likely to occur. This is because the more energy released , the more stable the daughter nuclues is , A heavy nucleus undergoes fission such that its producets will be more stable than the parent nucleus. |
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| 432. |
Mark out the incoreect statemnet.A. A free neutron can transfrom itself into photn.B. A free neutron can transfrom itself into neutron.C. In beta minus decay, the electron originates from nucleus.D. All of the above |
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Answer» Correct Answer - a When a free neutron along with an electron and an antineutino, the value of the reaction is positive which means the reaction is possible all by itslef, while a free proton cannot convert itself into a neutron due to negative `Q `value. In beta minus decay, the electron originates from nucleus only, by the transformation of neutron into a proton, with simultaneous emission of an antineutron. |
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| 433. |
Mark out the coreect statemnet (s).A. In fission and fusion processes, the mass of reactant nuclide is greater than the mass of product nuclide.B. In fission process, BE per nucleon of reactant nucleide is less than the binding energy per nucleon of product nucleide.C. In fusion process, BE per nucleon of reactant nucleide is less than the binding energy per nucleon of product nucleide.D. In fusion process, BE per nucleon of reactant nucleide is greater than the binding energy per nucleon of product nucleide. |
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Answer» Correct Answer - a,b,c, In general, fission and fusion processes are exothermic reactions, i.e., energy is released. Hence, mass of products must be less than mass of the reactant nuclide, and `BE//A` of reactants `lt BE//A` of products nuclides. |
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| 434. |
The half-life of `._92^238U` against alpha decay is `4.5xx10^9` year. How much disintegration per second occurs in `1 g` of `._92^238U`?A. `1.53xx10^(4)s^(-1)`B. `1.325xx10^(4)s^(-1)`C. `1.412xx10^(4)s^(-1)`D. `1.235xx10^(4)s^(-1)` |
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Answer» Correct Answer - D `N=(N_(0))/(2^(n))` |
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| 435. |
If a radioactive substance reduces to `(1)/(16)` of its original mass in `40` days, what is its half-life ?A. 10 daysB. 20 daysC. 40 daysD. None of these |
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Answer» Correct Answer - A (a) `(N)/(N_0) = ((1)/(2))^n rArr (1)/(16) = ((1)/(2))^4 = ((1)/(2))^n rArr n = 4` Also `n = (t)/(T_(1//2)) rArr T_(1//2) = (40)/(4) = 10 days`. |
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| 436. |
`99 %` of a radioactive element will decay betweenA. `6` and `7` half-livesB. `7` and `8` half-livesC. `8` and `9` half-livesD. `9` half-lives |
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Answer» Correct Answer - A (a) `N = N_0((1)/(2))^n rArr (N)/(N_0) = ((1)/(2))^n rArr (1)/(100) = ((1)/(2))^n ` `rArr 2^n =100` `n` comes out in between `6` and `7`. |
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| 437. |
Calculate the Q-value in the following decays: (a) `^19 O rarr ^19 F + e + vec v`. (b) `^25 A1 rarr ^25 Mg + e^+ + v`. The atomic masses needed are as follows : `^19 O 19.003576 u` `^19 F 18.998403 u` `^25 A1 24.990432 u` `^25 Mg 24.985839 u` |
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Answer» (a) The `Q`-value of `beta^(-)` decay is `= [m(.^(19)O)-m(.^(19)F)]c^(2)` `=[19.003576u-18.998403 u](931 MeV//u)` `=4.816 MeV` (b) The `Q`-value of `beta^(+)`-decay is `Q=[m(.^(25)Al)-m(.^(25)Mg)-2m_(e )]c^(2)` `=[24.99032u-24.985839u-2xx0.511(MeV)/(c^(2)]c^(2)` `=(0.004593u)(931MeV//u)-1.022 MeV` `=4.276 MeV-1.022 MeV=3.254 MeV.` |
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| 438. |
Which of the following isotopes is normally fissionable ?A. `._92 U^238`B. `._93Np^239`C. `._92 U^235`D. `._2 He^4` |
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Answer» Correct Answer - C ( c) `._92 U^235` is normally fissionable. |
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| 439. |
Assume that the nuclear binding energy per nucleon `(B//A)` versus mass number `(A)` is as shown in figure. Use this plot to choose the correct choice(s) given below. (a) Fusion of two nuclei with mass numbers, lying in the range of `1ltAlt50` will release energy. (b) Fusion of two nuclei with mass numbers lying in the range of `51ltAlt100` will release energy. (c) Fission of a nucleus lying in the mass range of `100ltAlt200` will release energy when broken into two equal fragements. (d) Fission of a nucleus lying in the mass range of `200ltAlt260` will release energy when broken into two equal fragments. A. `(i),(ii)`B. `(ii),(iii)`C. `(iii),(iv)`D. `(ii),(iv)` |
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Answer» Correct Answer - D In `(ii),(iv),B.E`./nucleon increses, enegry is released. |
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| 440. |
Which of the following statement `(s)` is/are correct (i) The rest mass of a stable nucleus is less than the sum of the rest masses of its separated nucleous (ii) The rest mass of a stable nucleus is greater than the sum of the rest masses of its separated nucleous (iii) In culear fusion, energy is released by fusion two nuclei of medium amss (approximaltely `100 "amu"`) (iv) In nuclear fussion, energy is released by freagmentation of a very heavy nucleusA. `(i),(iii)`B. `(ii),(iii)`C. `(i),(iv)`D. `(ii),(iv)` |
| Answer» Correct Answer - C | |
| 441. |
The stable nucleus that has a radius `1//3` that of `Os^(189)` is-A. `._(3)Li^(7)`B. `._(2)He^(4)`C. `._(5)B^(10)`D. `._(6)C^(12)` |
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Answer» Correct Answer - A Radius of `Os^(189)=r_(0)A_(os)^(1//3)` Radius of that nucleus `=(1)/(3)xxr_(0)(A_(o_(5)))(1)/(3)=r_(0)((189)/(27))^(1)/(3)=r_(0)7^(1//3)` `:. A` for that nucleus `=7` |
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| 442. |
The graph of `1n (R/R_0)` versus `1n A (R = radius` of a nucleus and `A =` its mass number) isA. a straight lineB. a parabolaC. am elliipseD. none of them |
| Answer» Correct Answer - A | |
| 443. |
For uranium nucleus how does its mass vary with volume?A. `m prop V`B. `m prop 1//V`C. `m prop sqrt(V)`D. `m prop V^(2)` |
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Answer» Correct Answer - A Nuclear density is constant hence, mass `prop` volume or `m propV` |
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| 444. |
Which of the following statements is true for nuclear forces?A. They obey the inverse square law of distance.B. They obey the inverse third power law of distanceC. They are short range forcesD. They are equal in strength to electromagntic forces |
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Answer» Correct Answer - C |
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| 445. |
If `M` is the mass of a nucleus and `A` is its mass number, then `(M -A)/(M)` is called itsA. binding energyB. Fermi energyC. mass defectD. packing fraction |
| Answer» Correct Answer - D | |
| 446. |
Fusion reaction takes place at high temperature becauseA. atoms get ionised at high temperatureB. kinetic energy is high enough to overcome the coulomb repulsion between nucleiC. molecules break up at high temperatureD. nuclei break up at high temperature |
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Answer» Correct Answer - B |
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| 447. |
In a beam of neurons the particles are having a kinetic energy of 0.0327eV. If the half life of neutron is 693 second. What fraction of neutrons will decay before the beam advances by 10m? Given mass of neutron `=1.675xx10^(27)kg`. |
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Answer» Correct Answer - `4xx10^(-6)` |
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| 448. |
For atomic nuclei, the binding energy per nucleonA. increases continously with increases in mass numberB. decreases continously with increases in mass numberC. remains constant with increases in mass numberD. first increases and then with decreases in mass number |
| Answer» Correct Answer - D | |
| 449. |
Which of the following is a wrong description of binding energy of a nucleus?A. It is the enegry required to break a nucleus into its constituent nucleousB. It is the enegry made available when free nucleons combine to from a nucleusC. It is the sun of the rest mass energies of its nucleons minus the rest mass energy of the nucleusD. It is the sun of kinetic energy of all the nucleons in the nucleus |
| Answer» Correct Answer - D | |
| 450. |
As the mass number `A` increases, the binding energy per nucleon in a nucleus.A. increasesB. decreasesC. remains the sameD. varies in a way that depends on the actual value of `A` |
| Answer» Correct Answer - D | |