Radioactivity Questions and Answers

The mean lives of a radioactive substance are 1600 years and 400 years for a emission and emission respectively The time during which three fourth of a sample decays if it is decaying both a and emissions simultaneously will be nearly 400 years 500 years 644 years 444 years

A Li target is bombarded with a proton beam currentof 10 Amp for 1hr to produce Be of activity 1 8 x 10 disc sec Assuming that one Be radioactive n cleus is produced by bombarding 1000 protons Determine the half life of Be h ob fa

c In 2 s 2 A radioactive isotope is being produced at a constant rate X Half life of the radioactive substance is Y After some time the number of radioactive nuclei become constant The value of this constant is b XY a An 2 c XY In 2 d X Y AS

Two radioactive substances x and y initially contain equal number of nuclei x has a half life of 1hour and y has a half life of 2 hours After two hours the ratio of the activity of x to that of y is 1 1 4 3 1 1 2 1 2 4 2 1

1 1 2 1 5 3 2 1 4 2 5 The fossil bone has a 14C 12C ratio which is 2002 1 16 of that in a living animal bone If the half pritlife of 4C is 5730 years then the age of the fossil bone is 1 11460 years 3 22920 years 2 17190 years 4 15840 10

6 67x 10 53 A radioactive material has mean lives of 1620 yr and 520 yr for a and emission respectively The material decays by simultaneous a and emission The time in which 1 4th of the material remains intact is a 4675 yr b 720 yr d 324 yr c 545 yr constant

A common example of decay is 15 P 32 x y 16P 32 Then x and y stand for a electron and neutrino b positron and neutrino c electron and antineutrino d positron and antineutrino

0 The plot of the number N of decayed atoms versus activity R of a radioactive substance is a c N b d R R

31 A radioactive sample has No active atoms at t 0 If the rate of disintegration at any time is R and the number of atoms is N then the ratio R N varies with time as c R N 0 b d R N O N

Suppose we consider a large number of containers each containing initially 10000 atoms of a radioactive material NCERT Exemplar with a half life of 1 yr After 1 yr a All the containers will have 5000 atoms of the material b All the containers will contain the same number of atoms of the material but that number will only be approximately 5000 c The containers will in general have different numbers of the atoms of the material but their average will be close to 5000 d None of the containers can have more than 5000 atoms ple is left undecayed after time

potential energy of electron in the 44 In a sample of radioactive material what fraction of the initial number of active nuclei will remain after half of the half life of the sample b 1 2 c 1 2 2 d 1 4 undisintegrated a 2 1 15 In a radioactive comple the fraction of initial number of

If in a nuclear fusion process the masses of the fusing nuclei be m and m and the mass of the resultant nucleus be M 3 then b m3 m m l d m3 m m 2004 a m3 m m c m3 m m

22 A sample of as iodine ion was administered to a patient in a carrier consisting of 0 10 mg of stable iodine ion After 4 days 67 7 of initial radioactivity was detected in the thyroid gland of the patient The percentage of stable iodine ion that had migrated to the thyroid gland if ty for iodide ion is 8 days is 1 65 8 2 95 7 3 85 8 4 75 8

The volume occupied by an atom is greater than the volume of the nucleus by a factor of about a 10 c 10 0 b 105 d 10 5 2003 A sample of radioactive element has a mass of 10 g at an instant t 0 The approximate

A radioactive element decays by emission A detector records n beta particles in first 2 seconds and 0 8 n beta particles in next 2 seconds Find the time in which 40 of the initially present nuclei will decay A 2 n 5 4 In 5 3 B 2 n 5 3 In 5 4 C 2 n 5 3 In 5 2 2 n 5 2 D In 5 3

5 In a nuclear reactor the number of U235 nuclei undergoing fissions per second is 4 x 1020 If the energy released per fission is 250 MeV then the total energy J EAMCET 2015 released in 10 h is 1 eV 16 x 10 19 a 576 106 J c 576 10 5J b 576 10 2J d 576 10 8 J is not found in Keral

11 If 20 of a radioactive element decays in 10 days then amount of original material left after 30 days is approx UP CPMT 2015 b 62 a 78 c 51 d 48 ucleus at rest splits into two nuclear parts having

The phenomenon of radioactivity a increases on applied pressure b is exothermic change which increases or decreases with temperature c is nuclear process which does not depend on external forces d None of the above hing 1 kg explodes releasing is

0 A radioactive substance has an average life of 5 hr In a time of 5 hours a Half of the active nuclei decay b Less than half of the active nuclei decay c More than half of the active nuclei decay d All active nuclei decay

52 After a certain lapse of time the fraction of radioactive A radic polonium undecayed is found to be 12 5 of the initial quantity What is the duration of this time lapse if half life of polonium is 139 days processe for the se half life a 417 days b 500 days c 420 days d 512 days

40 The activity of sample is 64 x10 5 Ci Its half life is 3 days The activity will become 5 10 Ci after a 12 days b 7 days c 18 days d 21 days 41 3 8 days is the half life

28 In a radioactive substance at t 0 the number of atoms is 8 x 10 Its half life period is 3 years The number of atoms 1 x 10 will remain after interval a 10 year b 9 year c 20 year 29 The half life peri d 3 year

C 20 year d 3 year 29 The half life period of radium is 300 years The fractio of sample of radium that would remain after 2700 yea is a 1 512 b 1 128 c 1 176 d 1 200

Assume that the atomic mass of sulphur is 16 A sample of 40 g of an oxide of uranium contains 36 g of uranium Which of the following formula for the sulphide is incompatible with the data A B C D Uranium sulphide is US2 and the atomic mass of U is 72 Uranium sulphide is U3S4 and the atomic mass of U is 108 Uranium sulphide is U4S3 and the atomic mass of U is 108 Uranium sulphide is US and the atomic mass of U is 144

A radioactive nucleus has specific binding energy E It emits an a particle The resulting nucleus has specific binding energy E Then a E E c E E b E E d E 0

The initial mass of the radioactive substance is 10 g What is left after 2 average lives a 2 5 g c 4 87 g b 6 8 g d 1 37 g AFMC it 103 Two rac constant same nu of A to 1 a

COMPREHENSION charged particle of charge q and mass m is projected with initial veloc from a distance a from the fixed charge Q at an angle of a 60 w qQ 4ne am the line joining the charges as shown in the figure It is found that the particle moves on elliptical orbit with the charge Q at one of its foci 13 The length of the semi major axis of the ellipse equals to JA a B a 2 a 3 D 2a

45 A 50 Co source is labeled 4 3 mCi but its present activity is found to be 1 71x107 Bq a What is the present activity in mci mci b How long ago in years did it actually have a 4 00 mCi activity

6 Fig 11 1 shows how the count rate from a radioactive source varies with time 60 count rate counts s 50 40 30 20 10 20 40 60 80 100 120 Fig 11 1 a Using Fig 11 1 describe how the count rate changes with time 140 time s 160 Activate V 2

A radioactive sample has decay constant 2 The rate of production of nuclei in the given sample 92N where No is the number of radioactive N nuclei in the sample at t 0 and N is the number of radioactive nuclei in the sample at time t t sec If the number of nuclei present in the radioactive sample at t is m x 106 nuclei then find the value of m Given N 106 nuclei as

104 A gas of monoatomic hydrogen is bombarded with a stream of electrons that have been accelerated from rest through a potential difference of 12 75 volt In the emission spectrum one cannot observe any line of b Balmer series a Lyman series c Paschen series d Pfund series BHU

A radio isotope X has a half life of 10s Find the number of active nuclei in the sample if initially there are 1000 isotopes which are falling from rest from a height of 3000 m when it is at a height of 1000 m from the reference plane Question Type Single Correct Type 1 50 2 250 3 29

A radioactive material decays by simultaneous emission of two particles with respective half lives 1620 and 810 years The time in years after which one fourth of the material remains is Question Type Single Correct Type 1 1080 2 2430

A nuclear reaction along with the masses of the particle taking part in it is as follows B C QMeV A 1 002 amu The energy Q liberated in the reaction is 1 004 amu 1 Question Type Single Correct Type 1 234 MeV D 1 003 amu 1 001 amu 2 0 931 MeV

19 There are two radioactive substances A and B Decay constant of B is two times that of A Initially both have equal number of nuclei After n half lives of A rate of disintegration of both are equal The value of n is a 1 c 4 b 2 d All of these

The graph shows some measurements of the decay rate of a sample of radio active nuclei 1281 Find the half life for this radioactive nucleus 6 2 In R R in counts s a 20 min c 15 min 50 100 150 200 225 Time min b 25 min d 75 s AMU Med

1 Half life of a radioactive element is the time required for the element to reduce to half of its initial concentration A t A where The rate of change of concentration is calculated by the formula is the half life of the material A is the initial concentration of the radioactive element in the given sample A t is the concentration of the radioactive element in the sample after time t If Radium has a half life of 1600 years and the initial concentration of Radium in a sample was 100 then calculate the percentage of Radium in that sample after 2000 years UTE OF TECHNOL 1 35 2 42 3 19 4 21

64 based ratio of U238 and Pb226 in a sample of rock is 4 3 If the half life of U238 is 4 5 10 years then the age of rock is a 9 0 10 years c 4 5 10 years b 6 3 10 years d 3 8 10 years Kornatelu OFT 71 At tim 1600 at t a c

9 A sample of a radioactive element whose half life is 30 s contains a million nuclei at a certain instant of time How many nuclei will be left after 10 s a 3 33 105 3 78 105 c 7 94 105 1 26 105 b d

When aluminium is bombarded with fast moving neutron it changes int sodium with emission of particle X according to equation 2 3 AI n 4Na X The particle X is Electron Proton Alpha particle Positron

16 A nucleus ruptures into two nuclear parts which have their velocity ratio equal to 2 1 What will be the ratio of their nuclear size nuclear radius 1 31 2 1 2 1 31 2 3 21 3 1 4 1 21 3 U 56

thorium and helium Then A nucleus of uranium decays at rest into nuclei of Re AIPMT 2015 1 The helium nucleus has less kinetic energy than the thorium nucleus 2 The helium nucleus has more kinetic energy than the thorium nucleus 3 The helium nucleus has less momentum than the thorium nucleus 4 The helium nucleus has more momentum than the thorium nucleus

The rate of radioactive disintegration at an instant for a radioactive sample of half life 2 2 x 109 s is 1010 s 1 The number of radioactive atoms in that sample at that instant is NEET 2019 Odisha 1 3 17 1019 2 3 17 x 1020 3 3 17 1017 4 3 17 1018

In the classic Meselson and Stahl experiment E coli are first grown in 15N enriched media 0th generation and subsequently switched to 14N media What is the ratio of 14N over 15N single stranded DNA in the third generation of E coli grown in 14N media assuming that replication occurs in a semiconservative fashion 31 15

1 Summarizing ionizing radiation Fill in the chart with the characteristics of ionizing radiation For Ionizing density and Penetrating ability indicate high medium or low What is it Particle alpha a beta B beta B gamma y Charge Ionizing density Penetrating ability

In the movie The Planet of the Apes the forbidden zone was an area presumably contaminated by the radioactive plutonium fallout from the detonation of nuclear weapons If Zera finds a rock in the forbidden zone that is tainted with plutonium 239 whose activity is 100 Bq how many atoms of plutonium does the rock contain when it is discovered Half life of plutonium 239 is 24 900 y

4 If the mass of a radioactive sample is increased the activity of the sample and decay constant of the sample respectively will NCERT Pg 447 1 Increase Increase 2 Decrease Increase 3 Increase Remain same 4 Remain same Remain same

Iwo radioactive substances A and B initially contain equal number of nuclei A has half life of 1 hour and B has a half life of 3 hour After 6 hour the ratio of activity of A to that of B is 1 3 3 16 H 2 4 13 15 5

Two samples X and Y contain equal 1 amount of radioactive substances If 16th 1 of the sample X and 256 of the sample Y remain after 8 hours then the ratio of half periods of X and Y is Question Type Single Correct Type 1 2 1

A freshly prepared radioactive source of half life 2 h emits radiation of intensity which is 64 times the permissible safe level The minimum time after which it would be possible to work safely with this source is a 128 h b 24 h c 6 h d 12 h