Nuclei

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