Half Life and Average Life
Trending Questions
Q. The half-life of a radioactive isotope X is 50 years. It decays to another element Y which is stable. The two elements X and Y were found to be in the ratio of 1 : 15 in a sample of a given rock. The age of the rock was estimated to be
- 100 years
- 150 years
- 250 years
- 200 years
Q. The mean lives of a radioactive substance for α and β emissions are 1620 years and 405 years respectively. After how much time will the activity be reduced to one fourth
- 405 year
- 449 year
- None of these
- 1620 year
Q. 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
- 12 hours
- 24 hours
- 128 hours
- 6 hours
Q. The counting rate observed from a radioactive source at t = 0 second was 1600 counts per second and at t = 8 seconds it was 100 counts per second. The counting rate observed as counts per second at t = 6 seconds will be
- 400
- 300
- 200
- 150
Q. At any instant the ratio of the amount of radioactive substances is 2 : 1. If their half lives be respectively 12 and 16 hours, then after two days, what will be the ratio of the substances
- 1 : 1
- 2 : 1
- 1 : 2
- 1 : 4
Q. The kinetic energy of a neutron beam is 0.0837 eV. The half-life of neutrons is 693s and the mass of neutrons is 1.675×10−27 kg. The fraction of decay in travelling a distance of 40m will be
- 10−3
- 10−4
- 10−5
- 10−6
Q. Half-life of a substance is 20 minutes. What is the time between 33% decay and 67% decay
- 20 minutes
- 30 minutes
- 40 minutes
- 25 minutes
Q. A sample of radioactive element has a mass of 10 gm at an instant t = 0. The approximate mass of this element in the sample after two mean lives is.
- 2.50 gm
- 6.30 gm
- 1.35 gm
- 3.70 gm
Q. The count rate of a Geiger- Muller counter for the radiation of a radioactive material of half life of 30 minutes decreases to 5s−1 after 2 hours. The initial count rate was
- 625 s−1
- 25 s−1
- 80 s−1
- 20 s−1
Q. 87Ra221 is a radioactive substance having half life of 4 days. Find the probability that a nucleus undergoes decay after two half lives
[IIT-JEE-2006]
[IIT-JEE-2006]
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