Nuclei

Four statements are given (A is mass number) : Choose the correct answer from the options given below :

1. A and D are true, but B and C are false
2. B and D are true, but A and C are false
3. B and C are true, but A and D are false
4. A and C are true, but B and D are false

An unknown nucleus has a nuclear density of 2.29 1017 kg/m3 and mass of 19.926 10-27 kg. Its mass number A is approximately : (Take R0 = 1.2 10-15 m, 4π = 12.56)

1. 16
2. 20
3. 12
4. 19

Consider the following nuclear reaction 238U 234Th + 4He Take masses of 238U, 234Th and 4He as 238.050 u, 234.043 u and 4.003 u, respectively. The Q value for the reaction, in keV, is: [Given: 1 u = 931.5 MeV c-2]

1. 3740
2. 3726
3. 3730
4. 3736

29082X Y e+ Z - P e- Q In the nuclear emission stated above, the mass number and atomic number of the product Q respectively, are

1. 280, 81
2. 286, 80
3. 288, 82
4. 286, 81

Water is used as a coolant in a nuclear reactor because of its

1. high thermal expansion coefficient
2. high specific heat capacity
3. low density
4. low boiling point

Select the correct statements among the following : Choose the most appropriate answer from the options given below :

1. A, B and C only
2. A, B and D only
3. A and B only
4. C and D only

The half life of a radioactive substance is 20 minutes. In how much time, the activity of substance drops to ( 116 )th of its initial value?

1. 40 minutes
2. 60 minutes
3. 80 minutes
4. 20 minutes

A nucleus of mass number 189 splits into two nuclei having mass number 125 and 64. The ratio of radius of two daughter nuclei respectively is

1. 1 : 1
2. 4 : 5
3. 5 : 4
4. 25 : 16

In the given nuclear reaction, the element X is 2211Na X + e+ +

1. 2311Na
2. 2310Ne
3. 2210Ne
4. 2212Mg

Given below are two statements In the light of the above statements, choose the most appropriate answer from the options given below :

1. Statement I is incorrect but statement II is correct
2. Both statement I and statement II are correct
3. Both statement I and statement II are incorrect
4. Statement I is correct but statement II is incorrect

At any instant, two elements X1 and X2 have same number of radioactive atoms. If the decay constant of X1 and X2 are 10 and respectively, then the time when the ratio of their atoms becomes 1e respectively will be :

1. 15
2. 111
3. 19
4. 16

A nucleus with mass number 240 breaks into two fragments each of mass number 120, the binding energy per nucleon of unfragmented nuclei is 7.6 MeV while that of fragments is 8.5 MeV. The total gain in the Binding Energy in the process is :

1. 216 MeV
2. 0.9 MeV
3. 9.4 MeV
4. 804 MeV

The half life of a radioactive nuclide is 100 hours. The fraction of original activity that will remain after 150 hours would be :

1. 23 2
2. 12
3. 12 2
4. 23

A radioactive nucleus ZAX Z-1B Z-3C Z-2D, where Z is the atomic number of element X. The possible decay particles in the sequence are :

1. -, , +
2. , -, +
3. , +, -
4. +, , -

The energy equivalent of 0.5 g of a substance is :

1. 4.5 1013 J
2. 1.5 1013 J
3. 0.5 1013 J
4. 4.5 1016 J

When a uranium isotope 23592U is bombarded with a neutron, it generates 8936Kr, three neutrons and :

1. 9140Zr
2. 10136Kr
3. 10336Kr
4. 14456Ba

For a radioactive material, half-life is 10 minutes. If initially there are 600 number of nuclei, the time taken (in minutes) for the disintegration of 450 nuclei is

1. 20
2. 10
3. 30
4. 15

Radioactive material 'A' has decay constant '8 ' and material 'B' has decay constant ' '. Initially they have same number of nuclei. After what time, the ratio of number of nuclei of material 'B' to that of 'A' will be e ?

1. 17
2. 18
3. 19
4. 1

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

1. 15
2. 30
3. 45
4. 60

A nucleus of uranium decays at rest into nuclei of thorium and helium. Then

1. The helium nucleus has more momentum than the thorium nucleus.
2. The helium nucleus has less kinetic energy than the thorium nucleus.
3. The helium nucleus has more kinetic energy than the thorium nucleus.
4. The helium nucleus has less momentum than the thorium nucleus.

If radius of the 2713Al nucleus is taken to be RAl, then the radius of 12553Te nucleus is nearly

1. 35 RAl
2. ( 1353 )1/3 RAl
3. ( 5313 )1/3 RAl
4. 53 RAl

The binding energy per nucleon of 73Li and 42He nuclei are 5.60 MeV and 7.06 MeV respectively. In the nuclear reaction 73Li + 11H 42He + 42He + Q the value of energy Q released is

1. 19.6 MeV
2. -2.4 MeV
3. 8.4 MeV
4. 17.3 MeV

A radioactive X with a half life 1.4 109 years decays to Y which is stable. A sample of the rock from a cave was found to contain X and Y in the ratio 1 : 7. The age of the rock is

1. 1.96 109 years
2. 3.92 109 years
3. 4.20 109 years
4. 8.40 109 years

A certain mass of Hydrogen is changed to Helium by the process of fusion. The mass defect in fusion reaction is 0.02866 u. The energy liberated per u is (given 1 u = 931 MeV)

1. 6.675 MeV
2. 13.35 MeV
3. 2.67 MeV
4. 26.7 MeV

The half life of a radioactive isotope 'X' is 20 years. It decays to another element 'Y' which is stable. The two elements 'X' and 'Y' were found to be in the ratio 1 : 7 in a sample of a given rock. The age of the rock is estimated to be

1. 80 years
2. 100 years
3. 40 years
4. 60 years

How does the Binding Energy per nucleon vary with the increase in the number of nucleons ?

1. Decreases continuously with mass number.
2. First decreases and then increases with increase in mass number.
3. First increases and then decreases with increase in mass number.
4. Increases continuously with mass number.

-particles, -particles and -rays are all having same energy. Their penetrating power in a given medium in increasing order will be

1. , ,
2. , ,
3. , ,
4. , ,

The half life of a radioactive nucleus is 50 days. The time interval (t2 - t1) between the time t2 when 23 of it has decayed and the time t1 when 13 of it had decayed is

1. 30 days
2. 50 days
3. 60 days
4. 15 days

If the nuclear radius of 27Al is 3.6 fermi, the approximate nuclear radius of 64Cu in fermi is

1. 2.4
2. 1.2
3. 4.8
4. 3.6

A mixture consists of two radioactive materials A1 and A2 with half lives of 20 s and 10 s respectively. Initially the mixture has 40 g of A1 and 160 g of A2. The amount of the two in the mixture will become equal after

1. 60 s
2. 80 s
3. 20 s
4. 40 s