If the activity of a radioactive sample drops to 1/32 of its initial value after 7.5 Hours, its half-life will be:
1. 3 Hours
2. 4.5 Hours
3. 7.5 Hours
4. 1.5 Hours
From a newly formed radioactive substance (Half-life 2 hours), the intensity of radiation is 64 times the permissible safe level. The minimum time after which work can be done safely from this source is:
1. 6 hours
2. 12 hours
3. 24 hours
4. 128 hours
The relation between λ and T1/2 is:
(T1/2 = half-life, λ → decay constant)
1.
2.
3.
4.
Half-lives of two radioactive substances A and B respectively are 20 min and 40 min. Initially, the samples of A and B have an equal number of nuclei. After 80 min the ratio of the remaining number of A and B nuclei is:
1. 1 : 16
2. 4 : 1
3. 1 : 4
4. 1 : 1
If the half-life of a radionuclide is 77 days, then its decay constant is:
1. 0.003/day
2. 0.006/day
3. 0.009/day
4. 0.012/day
If the half-life of a radioactive substance is 10 hours, then its mean life is:
1. 14.4 h
2. 7.2 h
3. 20 h
4. 6.93 h
The half-life of a radioactive substance is 20 minutes. The time between 20% and 80% decay will be:
1. 20 minutes
2. 40 minutes
3. 30 minutes
4. 25 minutes
In a radioactive substance at t = 0, the number of atoms is 8, its half-life period is 3 yr. The number of atoms equal to will remain after an interval of:
1. 9 yr
2. 8 yr
3. 6 yr
4. 24 yr
The half-life of a radioactive nucleus is 50 days. The time interval between the time when of it has decayed and the time when of it had decayed is:
1. 30 days
2. 50 days
3. 60 days
4. 15 days
In a radioactive material, the activity at time is and at a later time, is . If the decay constant of the material is , then:
1.
2.
3.
4.