Radioactivity Questions and Answers

A nucleus mx emits two alpha particle and two beta particles The resulting nucleus is m 4 y n 2 m 8 y n 1 m 8 y n 2 m 8

Deuteron in its ground state has a total angular momentum J 1 and a positive parity The corresponding orbital angular momentum L and spin Scombinations are L 0 S 1 and L 2 S 0 c L 0 S 1 and L 2 S 1 b L 0 S 1 and L 1 S 1 d L 1 S 1 and L 2 S 1

When a nucleus in an atom undergoes a radioactive decay the electronic energy levels of the atom O Change for a radioactivity but not for others O Change for B radioactivity but not for others Change for a and B radioactivity but not for Y radioactivity O Do not change for any type of radioactivity

29 64 Cu can decay by Bor B emission or electron capture It is known that Cu has a half life of 12 8 hrs with 40 probability of B decay 20 probability of decay and 40 probability of 29 64 28 64 29 electron capture The mass of 4 Cu is 63 92977 amu while Zn is 63 92914 amu and 2Ni is 63 92796 amu What is the half life for electron capture A 5 12 Hrs B 32 Hrs C 2 56 Hrs 64 30 D 16 Hrs

My and My denote the atomic masses of parent and daughter nuclei respectively in a radioactive decay The Q value for B7 decay is Q and that for decay is Q If me denotes the mass of an electron then which of the following statement is correct Q Mx My c Q Mx My 2m c O Q Q Mx My c Q Q Mx My 2me c

3 3 7 x 10 Bq 4 3 7 10 Bq The half life of 92U238 undergoing a decay 4 5 x 100 years The activity of 4 g sample of 92 UZ is INCERT Pg 448 1 1 23 10 Bq 2 1 23 x 105 Bq 3 4 9 10 Bq 4 49 1 1 mg radium has 2 68 x 10 8 atoms Its half radium atoms 105 Bq IT JER 12 The ener fission is 1 200 M 2 235 M 3 20 M 4 100 13 Pick out following 1 Be acc

My and My denote the atomic masses of the parent and the daughter nuclei respectively in a radioactive decay The Q value of decay is Q and that for decay is Q If me is mass of an electron then which of the following is correct O Q My My c O Q Mx My c

3 The original weight of a certain radioactive substance is 112 grams After 3 hours it decays to 56 grams Find the half life of this substance 4 If the half life of a substance is 50 years what fraction of a 200 gram substance remains after 200 years

Which of the following statements is false Question Type Single Correct Type 1 2 3 4 The energy spectrum of a decay is line spectrum The energy spectrum of particles is continuous The energy spectrum of y decay is continuous The energy spectra of a y decay are line spectra

29 NEET UG 2019 Odisha The rate of radioactive disintegration at an instant for a radioactive sample of half life 2 2 x109 1010 s 1 The number of radioactive atoms in that sample at that instant is 1 3 17 x 1020 3 3 17 x 1018 V MP0343 2 3 17 x 1017

NEET II 2016 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 11

36 A sample of radioactive substance decays simultaneously by two processes A and B with half lives 1 2h and 1 4 h respectively For the first half hour it decays with process A next one hour with process B and for further half an hour with both A and B If originally there are No nuclei then the Number nuclei after 2h of such decay N 1 N 28 2 3 No 26 4 No 25

11 Radioactive nuclei P and Q disintegrate into R with hal lives 1 month and 2 months respectively At time t 0 number of nuclei of each P and Q is xTime at which rate of disintegration of P and Q are equal number of nuclei of R is R 600 2 1 25 x 4 1 75 x X 15 X ticles and

sub A 42 Half life period of a sample is 30 min Its decay 4 fraction at instant t is and decay fraction at 5 9 instant t is then t t interval is 10 1 30 min 2 43 min

8 A certain substance decays to of its initial 1th 64 activity in 24 days The half life of the substance will be 1 6 days 3 3 days 2 4 days 4 2 days

Figure shows activity A of three different radioactive materials samples Labeled as I II and III verses time Using the given information Choose the correct options A Disintegration constant has maximum value for the material of sample II B Half life is maximum for the material of sample III C Disintegration constant has minimum value for the material of sample II D Half life is minimum for the material of sample III A

3 6 32 mm 4 5 8 mm 7 Half life of a radioactive substance is 20 min The time taken between 20 decay and 80 decay wil be min 1 20 3 30 min 2 40 min 4 25 min Met

4 tending to zero 2 12 Two radioactive sources A and B of half lives of 1 hour and 2 hours respectively initially contain the same number of radioactive atoms At the end of two hours their rates of disintegration are in the ratio of 1 1 4 3 1 2 2 1 3 Louby 4 1 1

Q 16 If 10 of a radioactive substance decays in every 5 years then the percentage of the substance that will have decayed in 20 years will be 1 40 2 50 3 65 6 4 34 4

0 A vessel contains a non linear triatomic gas If 50 of gas dissociate into individual atom then find new valu of degree of freedom by ignoring the vibrational mode and any further dissociation 1 2 15 3 5 25 P a 2 3 75 4 6 35

34 A graph is plotted between rate of disintegration and number of active nuclei What is half life of the radioactive substance Time in second N 1 3 s 2 3 3 in 2 s In 2 4 30 dN dt

A radioactive isotope of potassium has half life x and decays to a stable isotope of argon in a sample of moon rock If age of moon rock is y then the present ratio of potassium atoms to argon atoms is A B C 1 2x 1 2xlx 1 2xx 1

The activity of a sample of a radioisotope at some time is 10 7 mCi and 0 36 h later it is 7 80 mCl Determine the following a Decay constant in s 2 40 4 b Half life in h 2887 916 X How is the half life related to the decay constant h c Nuclei in the sample when the activity was 10 7 mCi

c days the activity of a radioactive sample is 6000 dps The activity reduces to 3000 dpm her 140 days The initial activity of the sample in dps is JEE 2004 d 24000 c 3000 b 9000 The time taken for the activity of a sample of 215 At to decay

30 The mean lives of a radioactive substance are 1620 and 405 years for B emission and B emission respectively The time after which three fourth of a sample will decay if it is decaying both by emission and B emission simultaneously will be years Take In 2 0 693

A heavy nucleus having mass number 200 gets disintegrated into two small fragments of mass numbers 80 and 120 If binding energy per nucleon for parent atom is 6 5 MeV and for daughter nuclei is 7 MeV and 8 MeV respectively then the energy released in the decay will be Question Type Single Correct Type 1 200 MeV 2 220 MeV 3 220 MeV 180 Mall

SolveLancer Test An element X of atomic number 98 undergoes alpha decays The constant rate of alpha decay is n particles per second Atomic mass number of X is 251 u If the element Y daughter nucleus has atomic mass of 239 u What is the mass of total number of alpha particles radiated in grams SolveLancer Test a 4 g b 12 g c 2x 10 2 g d 4 x 10 23 g

20 Two radioactive materials X and X2 have decay constants 5 and 2 respectively If initially they have the same number of nuclei then the ratio of the number of nuclei of X to that of X will be 1 e after a time a e a b C 1 2 2 d 1 42

7 The phenomenon of radioactivity is associated with 1 Decay of nucleus 2 Fussion of nucleus 3 Emission of electrons or protons 4 Rearrangement in the extra nuclear electron

1 A radioactive substance is being produced at a constant rate of 200 nuclei s The decay constant of the substance is 1 s After what time the number of radioactive nuclei will become 100 Initially there are no nuclei present a 1 s c In 2 s b 1 In 2 loun d 2 s S

22 The radioactivity of an old sample of whisky due to tritium half life 12 5 years was found to be only about 4 of that measured in a recently purchased bottle marked 10 years old The age of sample is years

At a given instant say t 0 two radioactive A B have equal activities The substance RB ratio RA of their activities after time t is e 3t If half life of A is ln 2 then half life of B is Question Type Single Correct Type 1 2 3 en 2 2 2ln 2 en 2 4

After a perfectly elastic collision of two identical balls one of which was initially at rest the velocities of both the balls are non zero The angle 0 between the final velocities in the lab frame is b a 0 T 2 c 0 0 TC 2 d T 0

A black body which is at a high temperature T K emitted thermal radiation at the rate of E watt m The thermal radiation emitted by a body of emissivity equal to 0 5 at temperature T 4 in NCERT Pg 295 watt m is 1 E 512 2 E14 3 E 256 4 E 128

238U decays in 14 steps that together constitute the net reaction 238 U 206 Pb 60 8 He The sign represents some unknown particle particles Take 1 amu 931 5 MeV C The atomic masses of 238U 206Pb 4He are 238 050783u 205 974449u and 4 002603u respectively The Q value of the reaction is O 2 6 MeV O 4 4 MeV O 51 7 MeV 8 9 MeV k

In a radioactive reaction an unstable nucleus A dis integrates into a stable nucleus B But A is generated at a constant rate of q nucleus per second Then at steady state number of nucleus of A will be q sec A q2 Select an answer B 9 C A Parent Nucleus 9 2 B Daughter Nucleus

At any instant the ratio of the amount of radioactive substances is 2 1 If their half lives be respectively 12 and 16 hours then after two days what will be the ratio of the substances Question Type Single Correct Type 1 1 1 2 2 1 3 1 2

The binding energy per nucleon of deuteron and d par respectively The energy released in the following reaction will be 1H 1H 2He4 Q x1 x2 x2 x1 O 2 x1 x2 A X X

4 BA 40 40 If 10 of a radioactive material decays in 5 days then the amount of original material left after 20 days is approximately 1 60 2 65 4 82 1 60 3 70 410 fra 20 fe affer 2 65 4 75

3 250 years 4 100 years 10044 The rate of disintegration of a fixed quantity of a radioactive 6 fafter that are a face element can be increased by 1 increasing the temperature 2 increasing the pressure 3 chemical reaction 4 it is not possible 1 2 3 erfaren fafarangri 4

A radioactive sample contains two different types of radioactive nuclei A with half life 5 0 days and B with half life 30 0 days Initially the decay rate of the A type nuclei is 64 times that of B type of nuclei Their decay rates will be equal when time is n days Find the value of n

10 A radioactive nucleus X decays to a nucleus Y with a decay constant x 0 1s X Y further decays to a stable nucleus Z with a decay constant y 1 1 s Initially there 30 are only Xs nuclei and their number is N 102 Set up the rate equations for the populations of X Y and Z The Populations of Y nucleus as a function of time is given by Ny t Nox exp 2 1 exp 2 1 Find the time at which N is maximum 2x 2y and determine the populations of X and Z at that instant

The half life of a radioactive nucleus 100 days The time interval h b between t time to when half of it has decayed and the time when three fourth of it had decayed is 1 60 days 2 15 days 3 30 days 4 100 days

Determine the factor by which amplitude of an oscillation decreases after 5 cycles whe he period of oscillation changes from 1 500 s to 1 502 s due to application of dampin orce a 0 198 b 0 584 c 0 326 d 0 424

Two radioactive materials X and X have decay constants 10 and respectively If initially they have the same number of nuclei if the ratio of the number of nuclei of X to that of X will be 1 e 9 after a time Find the value of n n

A radioactive sample has a half life of 40 seconds When its activity is measured 80 secon after the begining it is found to be 6 932 x 10 8 dps During this time total energy released 6x 10 joule n2 0 6932 A The initial number of atoms in the sample is 1 6 10 B The initial number of atoms in the sample is 1 6 1021 C Energy released per fission is 5 x 10 13 J D Energy released per fission is 558 10 3 J

ction E Nuclear Fission and Fusion 92U 235 nucleus absorbs a slow neutron and undergoes fission into 54X139 and 38 Sr94 nuclei The other particles produced in this fission process are A 1 B and 1 a B 2 B and 1 neutron neturons D 3 neutrons combing to form a carbon 120

Velm B M M Two radioactive sources A and B initially contain equal number of radioactive atoms Source A has a half life of 1 hour and source B has a half life of 2 hours At the end of 2 hours the ratio of the rate of disintegration of A to that of B is A 1 2 B 2 1 1 1 T 4 amount initially P and Q of a radioactive substance

It is now believed that protons and neutrons which constitute nuclei of ordinary matter are themselves built out of more elementary units called quarks A proton and a neutron consist of three quarks each Two types of quarks the so called up quark denoted by u of charge 2 3 e and the down quark denoted by d of charge 1 3 e together with electrons build up ordinary matter Quarks of other types have also been found which give rise to different unusual varieties of matter Suggest a possible quark composition of a proton and neutron

A photon with an energy of 4 9 eV ejects photoelectrons from tungsten When the ejected electron enters a constant magnetic field of strength B 2 5 mT at an angle of 60 with the field direction the maximum pitch of the helix described by the electron is found to be 2 7 mm Find the work function of the metal in electron volts Given that specific charge of electron is 1 76x10 Ckg wwsex