Radioactivity Questions and Answers

Compare between Stimulated Emission and Spontaneous Emission Higher energy as a total output Spontaneous Emission Stimulated Emission Need energy to starts Needs no energy to starts Follows Boltzman s distribution

1 Probability of decay of a particular nucleus of substance Z in next 1 hour is 3 of decay of a nucleus of same substance 1 1 A In next hours is 2 C In next 3 hours is 1 3 B In next 2 hours is D In next 1 5 hour is 9 1 3 Then probabil

Half lives of two radioactive substances A and Bare 20 hours and 40 hours respectively Initially the sample of A and B have equal number of nuclei The ratio of remaining number of A to that of B nuclei after 80 hours is 1 2 1 4 1 8

The rate of disintegration of a radioactive substance falls from 800 decay min to 100 decay min in 6 hours The half life of the radioactive substance is wala man as fave a 6 mil 800 y 100 cha OPTIONS MARK FOR REVIEW CLEAR SELECTION OA B 6 7 hour 2 hrs

FINDING HALF LIFE OF RADIOACTIVE NUCLEI The half life of a radioactive isotope X is 50 years It decays to another element Y which is stable The two elements X and Y were found to be in the ratio of 1 15 in a sample of a given rock The age of the rock was estimated to be a 150 years c 250 years b 200 years d 100 years

Two identical samples same material and same amount initially P and Q of a radioactive substance having mean life T are observed to have activities Ap Aq respectively at the time of observation If P is older than Q then the difference in their ages is A Ten B Ten Ap Ap Aa Ap C en A Ap D T Ap Aq

In one dimension a random walker takes a step with equal probability to the left or right What is the probability that the walker returns to the starting point after 4 steps a 3 8 b 5 16 c 1 4 d 1 16

Half lives of two radioactive substances A and B are 20 hours respectively Initially the sample of A and B have equal number of nuclei The ratio of remaining number of A to that of B nuclei after 80 hours is 01 2 01 4 0 1 8 01 16

If activity of a radioactive substance is Ro at time t 0 and R at t 10 hours then the time in hours at which the activity reduces to half 5 log10 2 5 loge 2 5 log 2 5 log 2 2 of its initial value is

1 A radioactive sample of half life 23 1 days is 2 disintegrating its in 15th to 16th days will be Take e0 03 1 03 a 5 b 1 continuously The percentage decay of c 2 9 d 3 5

175 Which of the following fusion reactions will not result in the net release of energy 1 Li Li 3 2C C a 1 b 2 2 He He 35 CI 35 CI 4 c 3 d 4 AMU Med 2014 2013

A radioactive sample S1 having an activity of 5uCi has twice the number of nuclei as another sample S2 which has an activity of 10uCi The half lives of S1 and S2 can be 1 20 years and 5 years respectively 2 20 years and 10 years respectively 3 10 years each 4 5 years each The half life period of a radioactive substance

A fresh radioactive sample is given at t 0 Its decay fraction are at t instant and L instant Its mean life is 1 4 4 n2 2 n4 424 415 at 4 15 4

A nuclear reactor takes 30 days to use upto 2 kg of fuel of 92U235 and each fission gives 185 MeV of usable energy The power output of this reactor is 58 5 MW 40 6 MW O 120 3 MW 100 MW

tially 98 grams of radioactive substance was present After 2 hours the mass had decreased by 6 If the rate of decay is proportional to e amount of the substance present at a time t Find the amount remaining after 39 hours und your answer to 2 decimal places

A radioactive isotope A with a half life of 1 25 x 10 year decays into B which is stable A sample of rock from a planet is found to contain both A and B present in the ratio 1 15 The age of the rock is O 4 x 107 year O 5 10 year O 5 x 10 0 year hr min 4 x 10 1 year

A radio nuclide with half life T days emits p particles of average kinetic energy E joule This radionuclide is used as source in a machine which generates electric energy with efficiency n The no of moles of the nuclide required to generate electrical energy at an initial rate P is Avagadro no N

38 The total radiative power emitted by spherical blackbody with radius R and temperature T is P If the radius if doubled and the temperature is halved then the radiative power will be a P 4 c 2P b P CONGRIAN 2 d 4P

At 500 K equilibrium constant Kc for the following reaction is 5 H2 g 1 12 g HI g 2 What would be the equilibrium constant K for the reaction 2HI g H2 g 12 g Question Type Single Correct Type 1 0 04 2 0 4 3 25

The half life for beta decay of cesium 137 is 30 years A water sample is found to contain 10 ppm cesium 137 How many months would pass before the cesium 137 concentration would drop to 2 ppm 1 ppm 1 particle per million

39 A certain radioactive isotope has a half life of 2 days If 8 kg of the isotope is placed in sealed container how much of the isotope will be left after 8 days a 1 kg c 0 5 kg b d 2 kg 4 kg

The age of an organic material is usually determined by measuring its 14C content carbon dating The ratio of the number of stable isotope of 14C atoms present to the number of radioactive 14C atoms in a material is found to be 3 1 If the half life of 14C atoms is 5730 years the age of the material under investigation is 7944 years 17190 years 11460 years 13972 years

Which statement about radioactive radiations is true A Speed of a particles is a characteristic property B Speed of particles is a characteristic property C Speed of y photon is a characteristic property D All of these

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 NEET Phase 2 2016 1 15 3 45 2 30 4 60

38 Radioactive nuclei X and Y disintegrate into Z with half lives to and 2t respectively Initial number of both X and Y No Time at which rates of disintegration of X and Y are equal number of nuclei of Z is 1 3 3No 4 5No 4 2 4 No 4 7No 4

47 A freshly prepared sample contains 16x1020 radioactive nuclei whose mean life is 10 0 seconds The activity of the sample just after 4 half lives time is In 2 a x1010 dps 16 1 c x10 0 dps In 2 b 1x10 0 dps d In 2x10 0 dps

45 In a certain nuclear reactor a radioactive nucleus is being produced at a constant rate 1000 s The mean life of the radionuclide is 40 minutes At steady state the number of radionuclide will be a 4 104 b 24 x 104 c 24 x 105 d 24 106

Initially 500 milligrams of a radioactive substance were present After 3 days the mass had decreased by 145 milligrams If the rate of decay is proportional to the amount of the substance present at time t find the amount remaining after 10 days rounded to the nearest milligram Present your work in an organized manner and Box your Final Answer

6 The ratio between total acceleration of the electron in singly ionized helium atom and hydrogen atom both in ground state is a 1 c 4 b 8 d 16

3 A radioactive substance X decays into another radioactive substance Y Initially only X was present Ax and y are the disintegration constants of X and Y Nx and Ny are the number of nuclei of X and Y at any time t Number of nuclei Ny will be maximum when a Ny y Nx Ny x 2y x Nx NX Ny 2x 2y b e 2 Ny 2xNx d N 2 2

3 A radioactive isotope A decays into another isotope B which has a half life equal to 1 2 of that of A Both isotopes emit a particles during their decay and B decays into a stable nucleus If a sample consists initially of atoms of A only then the net activity of the sample initially a increases with time b decreases with time c remains constant d any of the above may be true ODON

The activity of a radioactive element decreased to one third of original activity Io in 9 yr After further 9 yr its activity will be A Io B 10 Your Answer C 10 9

Question No 33 Single Correct ENGLISH A radioactive element X disintegrates into a stable element Y with half life 2 year A fresh sample of X is available at t 0 At whic instant ratio of nuclei of X to nuclei of Y becomes 1 7 in the given sample A B C D t 8 yr t 6 yr t 14 yr Maximum Mark 4 00 t 2 yr

113 90 of the active nuclei present in a radioactive sample are found to remain undecayed after 1day The percentage of the undecayed nuclei left after two days will be A 85 C 80 B 81 D 79

Maximum kinetic energy of a particle Calculate the maximum kinetic energy of the beta particle emitted in the following decay process 12N12C e 12C Take atomic mass of 12N 12 018613 amu 12C 12 00000 amu m 0 00055 amu 8 y 12C y 4 43 MeV

Moderate 4 1 00 16 Pick out the unmatched pair from the following Moderator Heavy water Nuclear fuel C to C Pressurized water reactor water as the heat exchange system

1 A radioactive simultaneously O O X 2 X X 4 nucleus can decay by two different processes which have decay constant Aanda The effective decay constant of the nuclide is where 1 00 18

4 Increases but mass number remains same 157 Activity of a radioactive substance decays from 8000 becquerel to 4000 becquerel in 5 days Activity of the substance after next 10 days will be 1 500 becquerel 2 1500 becquerel 3 2000 becquerel 4 1000 becquerel

U 92 A fission reaction is given by 226 U 94 140 Xe 39 Sr x y 54 where x and y are two particles Considering 226U to be 92 Sr at rest the kinetic energies of the products are denoted by Kxe Xe Ksr Kx 2MeV and K 2MeV respectively Let the binding energies per nucleon of 236U 40 Xe and 3 Sr be 7 5 MeV 8 5 MeV and 8 5 MeV respectively Considering different conservation laws the correct option s is are 94 38 92 54 JEE 2015 a x n y n Ksr 129 MeV Kxe 86 MeV Sr Sr b x p y e Ksr 129 MeV K xe 86 MeV c x p y n Ksr 129 MeV Kxe 86 MeV

Springboard diving is a water sport in which a diver has to jump from a springboard that is situated at a certain height before diving into a swimming pool The length of the board is varied from 5 0 m to 10 0 m Its mass per unit length is 1 5 kg m and supported by two pillars Given that the minimum weight of the diver is 70 kg sketch and design a suitable platform so that the diver can jump at the end of the springboard without any problem The design should include the forces of the pillars to support the weight of the diver the distance between pillars and the torques of the system

Radioactive material A has decay constant 8 X and material B has decay constant X Initially they have same number of nuclei After what time the ratio of number of nuclei of material A to that B will be 1 e Question Type Single Correct Type 1 2 3 7X 1 8X 1 9X

View In English The half life of a radioactive isotope X is 25 years It docays to another element Y which is stable The two elements X and Y were found to be in the ratio of 1 15 in a sample of a given rock The age of the rock was estimated to be 1 2 3 4 ct Answer 4 unattempted dd to Bookmark Ust 150 years 200 years 250 years 100 years

Define the thickness of the water shield needed to reduce the intensity of monochromatic y radiation with the photon energy of 200 keV by a factor of 10 The linear attenuation coefficient for water at 200 keV is 1 36 cm 1 Choose one answer O 0 6 cm O 4 2 cm 02 4 cm O 1 7 cm

Energy released in the fission of a single 92U235 nucleus is 200 MeV The fission rate of a 92U235 fuelled reactor operating at a power level of 5W is 1 56 x 10 10 S 1 1 56 x 10 11 s 1 56 10 16 S 1 1 56 x 10 17 s 1

2 For a radioactive material half life is 10 minutes If initially there are 600 number of nuclei the time taken in minutes for the distintegration of 450 nuclei is a 30 2018 b 10 c 20 d 15

Two radioactive materials X and X have respectively If decay constants 5A and initially they have the same number of nuclei then the ratio of the number of nuclei of X to that of X2 will be 1 e4 after a time Question Type Single Correct Type 1 1 4X 2 1 A 3

A certain radioactive material is known to decay at a rate proportional to the amount present If initially there are 100 milligrams of the material present and if after two years it is observed that 5 percent of the original mass has decayed find a an expression for the mass at any time t and b the time necessary for 10 percent of the original mass to have decayed 7 3

Q 39 A nucleus with mass number 220 initially at rest emits an a particle If the Q value of the reaction is 5 5 MeV calculate the kinetic energy of the a particle 4 4 MeV 5 4 MeV 5 6 MeV FMV

46 A sample of radioactive element has a mass of 10 gm at an instant t 0 The approximate mass of this element in the sample after two mean lives is 2003 a 1 35 gm c 3 70 gm b 2 50 gm d 6 30 gm

28 A radioactive source in the form of a metal sphere of diameter 3 2 x 10 3 m emits B particles at a constant rate of 6 25 1010 particles sec The source is electrically insulated and all the B particles are emitted from the surface The potential of the sphere will rise to 1 V in time domu c 18 s mung a 180 s b 90 s d 9 s