Radioactivity Questions and Answers

The half life of 238U undergoing a decay is 4 5 x 10 years The activity of 1 g sample of U is a 1 23 x 10 Bq b 1 23 x 10 Bq c 1 23 x 10 Bq d 1 23 x 10 Bq

1 mg radium has 2 68 x 10 8 atoms Its half life is 1620 years How many radium atoms will disintegrate from 1 mg of pure radium in 3240 years a 2 01 10 c 1 01 x 10 b 2 01 x 10 8 d 1 01 10 8

21 Compute the activity of one gram of decay constant is 1 58 x 10 18 1 number 6 02 x 1023 mole Hint R luc whose Take Avogadro s dN dt 3 7 x 104 disintegrations s N Ans 0 11 uc microcurie 22 The half life of a radioactive material is 40 days What time will it take for the activity to drop to 30 of its initial value loge 2 0 6931 and loge 10 3 1 20 R N Ans 69 2 days

A radioactive sample S1 having an activity 5uCi has twice the number of nuclei as another sample S2 which has an activity of 10 Ci The half lives of S1 and S2 can be A 20 years and 5 years respectively 2008 C 10 years each B 20 years and 10 years respectively D 5 years each

A 280 days old radioactive substance shows an activity of 6000 dps 140 days later it s activity becomes 3000dps What was its initial activity A 20000 dps C 12000 dps B 24000 dps D 6000 dps 2004 100

material of half life 18 days inside the laboratory Tests revealed that the radiation was 64 times An accident in a nuclear laboratory resulted in deposition of a certain amount of radioactive more than the permissible level required for safe operation of the laboratory What is the 2016 minimum number of days after which the laboratory can be considered safe for use A 64 B 90 D 120 C 108

1 200 MeV 2 160 MeV In a radioactive decay let N be the number of residual active nuclei D the number of daughter nuclei R the rate of decay and M the mass of active sample at any time t Below are shown four curves NA DA r II I The correct ones are 1 III and IV RA L III 2 II III and IV IV 3 II IV and I 4 All of these

Initially a black body at absolute temperature T is kept inside a closed chamber which is at absolute temperatu To Now the chamber is slightly opened to allow sun rays to enter After opening the chamber it was observ that temperature T and To remains constant Which of the following statement s is are correct A The rate of emission of energy from the black body remains constant B The rate of emission of energy from the black body increases C The rate of absorption of energy from the black body increases D The energy radiated by the black body equals the energy absorbed by it

27 A body is thrown with a velocity equal to n times the escape velocity v Velocity of the body at a large distance away will be 1 ve n 1 2 v n 1 3 ve 1 n 4 None of these

0 At a certain instant a piece of radioactive material contains 10 2 atoms The half life of the material is 30 days i Find the number of disintegrations in the first second ii What time would elapse before 10 atoms remain iii What is the count rate after this time

The rate of 0 04 mol first c er reaction is s1 at 10 seconds and 0 03 mol 15 1 at 20 seconds after initiation of the reaction The half life period of the reaction is 1 24 1 s 2 34 1 s 3 44 1 s 4 54 1 s

Example 27 8 At time t 0 number of nuclei of a radioactive substance are 100 Att 1s these numbers become 90 Find the number of nuclei at t 2 s remained

6 Calculate the energy in fusion reaction 2H H2He n where BE of H 2 23 MeV un and of He 7 73 MeV Delhi 2016 1M

If concentration of A is 0 1 M at 5 sec then from following graph the rate constant is 10 77s 30 5 77 s 5sec 2 35 15 1 rigid container

The value of Z and A in the following reaction are respectively 92 U238Th Pa U RaA 1 88 230 3 90 230 a Z a a Rn Rn Po 2 88 226 4 90 226 a TE

The half life of radium is 1620 yr and its atomic weight is 226 g mol The number of atoms that will decay from its 1 g sample per second will be Avogadro s number N 6 023 x 1023 atom per mole b 3 61 x 10 2 Bq d 31 1 x 10 5 Bq a 3 61 x 10 0 Bq c 3 11 x 10 5 Bq

13 31 Suppose India has a target of producing by 2020 A D 200 000 MW of electric power 10 percent of which is to be obtained from nuclear power plants Suppose we are given that on average the efficiency of utilisation i e conversion to electric energy of thermal energy produced in a reactor is 25 How much amount of fissionable uranium would our country need per year at the turn of this century Take the heat energy per fission of U235 to be about 200 MeV Avogadro s Number N 6 023 x 1023 mol 1

83 Which one of the following graphs could represent the distribution p E of energies E of a particles emitted from a given source 1 3 P E P E 0 E AW E 2 4 p E p E 0 0 E E

Half life of a radioactive material is 69 3 hrs It s activity at t 0 is 50 Ci Find number of nuclei decayed between t 10 hours to t 11 hours 1 6 66 x 10 3 0 66 x 105 2 3 6 x 107 4 51 x 106

A sample of radioactive material A that has an activity of 10mCi has twice the number of nuclei as another sample of a different radioactive material B which has an activity of 20mCi The correct choice of half life of A and B would then be respectively 1 20 days and 5days 2 20 days and 10 days 3 5 days and 10 days 4 10 days and 40 days

The power obtained in a reactor using U235 disintegration is 1000 kW The mass decay of U235 per hour is 106 Amx 931 1 1 microgram 3 20 microgram 2 2 10 microgram 4 40 microgram

ET AIIMS The count rate of a Geiger Muller counter for the radiation of the a radioactive material of half life of 30 minutes decreases to 5 second 1 after 2 hours The initial count rate was 1 80 second 1 20 second 1 2 625 second 1 4 25 second 1

Mock Test The radioactivity of a sample is R at a time T and R at a time T If the half life of the specimen is T then number of atoms that will disintegrate in the time T T is equal to 1 R T R T 2 R R 3 R R T 4 R R T In 2

There is a stream of radioactive sample with velocity of 8 x 103 m s If the half life of radioactive sample is 1 sec then the fraction of sample which will decay before they travel a distance of 16000 m is 2 12 1 2 4 22 1 3

the force assumed equal for both the friends exerted by each friend on the road increases as the man moves up Find the force when the man is at a depth h cesoa 9F CO 2 Mg mg Figure 3 ma Tu ato 16 Love 18 19

The mean lives of a radioactive substance are 1620 years and 405 years for a emission and emission respectively The time during which three fourth of a sample will decay if it is decaying both by a emission and B emission simultaneously is a 339 years c 559 years b 449 years d 669 years

sample is The activity of a radioactive measured as No counts per minute att 0 and No e counts per minute at t 5 min The time in minute at which the activity reduces to half its value is CBSE AIPMT 2010 5 a log 2 5 b c 5 log 02 d 5log 2 log 2

A radioactive source in the form of a metal sphere of diameter 10 m emits B particles at a constant rate of 6 25 1010 particles per second If the source is electrically insulated how long will it take in us for its potential to rise by 1 0 volt assuming that 80 of emitted B particles escape from the surface

How many a and particles are emitted when 92 U238 decays into 82Pb206 1 8a 2p 3 8a 6p 2 7a 2 4 7a 1B

Which of the following reactions represents a fusion reaction 00 N e O 335U n 14 Ba Kr 3n 92 56 36 O 2 H He n O H He e

Which one of the following statements about nuclear reactions is false Select one O They are often accompanied by the release of enormous amounts of energy O O O Rate of reaction is independent of the presace of a catalyst Rate of reaction is independent of temperature Particles within the nucleus are involved No new elements can be produced

Question 14 A machine called an accelerator can be used to send gamma rays into specific par the human body to destroy cancer cells Which statement best describes this proc The machine uses the photoelectric effect to generate images of a patient s organs O The machine uses nuclear decay to treat cancer patients with radiation therapy O The machine uses nuclear decay to generate diagnostic images of cancer patients O The machine uses the photoelectric effect to introduce photons into a patient s organs

Six protons and six neutrons are brought together to form a carbon nucleus but the total mass of the carbon nucleus is less than the sum of the masses of the individual parts What has happened to the missing mass the mass defect it has been thrown off during radioactive decay O it has been converted into electrons O it has been emitted as light O it has been converted into the binding energy of the nucleus

It s estimated that a star with the mass of our sun will take about 10 billion years to consume all its core hydrogen fuel What s a reasonable estimate for how long a star with 0 3 times the sun s mass will take to consume all of its core hydrogen Select one OA 300 million years OB 3 billion years OC 20 billion years O D 70 billion years

A Nickel 59 has a decay constant of 2 89x10 13 s Calculate the half life B An initial sample of Nickle 59 has a mass of 14 3kg Calculate the time it will take for only 0 894kg of the parent isotope to rem

During work with a radioactive source a worker was told that he would receive 35 mrem at a distance of 4 5 m during 20 min of work What would be the received dose if the worker moved closer to 1 5 m for the same period

Consider an unlikely equilibrium situation where Ip Id parent and daughter have the same half life What would be the total activity

Use the graph below to answer the following question of substance remaining Fraction of Radioactive Nuclei Remaining 1 00 0 75 0 50 100 0 25 0 00 75 50 25 Use the graph below to answer the following question 0 0 Decay of a radioactive substance 19 How many half lives must this element undergo if there is 25 of the parent element remaining 1 2 6 7 5 6 3 4 5 Number of half lives 2 8 Radioactive Decay 3 4 Time in Years 9 5 10 20 How many years does it for one half life for this element 7 8

Due Wednesday May 4 Reminder Please fill out the course evaluation if you didn t during class Wednesday May 4 1 Rocks brought back from the Moon were estimated to have 8 of the 40K Potassium that it initially had It turns into 40 Ar How long ago were these rocks formed This indicates how long it has been since the Moon was hot and molten 2 a After 10 000 years what fraction of a sample of 40K is left over b After 1 000 years what fraction of a sample of 40K is left over c After 10 000 years what fraction of a sample of 14C is left over d After 1 000 years what fraction of a sample of 14C is left over

Due wednesday May Reminder Please fill out the course evaluation if you didn t during class Wednesday May 4th 1 Rocks brought back from the Moon were estimated to have 8 of the 40K Potassium that it initially had It turns into 40 Ar How long ago were these rocks formed This indicates how long it has been since the Moon was hot and molten 2 a After 10 000 years what fraction of a sample of 40K is left over b After 1 000 years what fraction of a sample of 40K is left over c After 10 000 years what fraction of a sample of 14C is left over

1 A sample of Lead 214 undergoes the following decay in order Give the symbol atomic mass and atomic number of the resulting isotope a Beta Decay b Beta Decay

2 The half life of Lead 214 is 1584 s a What is the decay constant for Lead 214 b A 100 0 kg sample of Lead 214 is allowed to decay for 4752 s How many kg of Lead 214 remain after that time

What is the missing product of the following Fusion reaction N H F 140

It is estimated that the Sun produces around 3 846x1026J of energy per second How much mass does the Sun convert to Energy every second 3 41x1043kg 1 28x1018 kg 4 27x10 kg 1 28x10 0kg

1 point What is the decay rate of a sample of Nitrogen 17 if the sample has 2 53x1018 atoms and a decay constant of 0 0972 s 2 60x101 Bq 3 85x10 20Bq 2 46x1017Bq

Scientist have the dream of producing enough energy in fusion reactors to power the needs of the entire country The US used about 1 37x1016J of energy in 2005 How much mass would have to be converted to energy to provided that much energy 1 239x1033 kg 4 57x107kg 1 27x1080kg 0 152kg

9 21x1018 atoms of Titanium 44 decay until only 2 30x1018 atoms remain How many half lives has passed 2

What is the decay constant for Beryllium 11 if it has a half life of 13 8s 0 0502 s 9 56s 0 0725 s

What is the half life of nobellium 253 if the decay constant is 0 00714 s 0 0103s 000 280 s 97 0s 0 00494s

L A sample of Lead 214 undergoes the following decay in order Give the symbol atomic mass and atomic number of the resulting isotope a Beta Decay b Beta Decay c Alpha Decay