Nuclei

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. +, , -