Advertisements
Advertisements
Question
A sample of old wood shows 7.0 dps/g. If the fresh sample of tree shows 16.0 dps/g, how old is the given sample of wood? (Half-life of 14C is 5730 y)
Advertisements
Solution
Given: t1/2 of 14C = 5730 y
`(- "dN"_0)/"dt" = 16`dps/g
`(- "dN")/"dt"` = 7 dps/g
To find: Age of sample of wood
Formulae:
- `"t"_(1//2) = 0.693/lambda`
- `lambda = 2.303/"t" log_10 ("N"_0/"N")`
Calculation:
`lambda = 0.693/"t"_(1//2) = 0.693/5730 = 1.209 xx 10^-4 "y"^-1`
`"t" = 2.303/lambda log_10 ("N"_0/"N")`
`= 2.303/(1.209 xx 10^-4) log_10 (16.0/7.0)`
= 6839 y
The age of sample of old wood is 6839 y.
APPEARS IN
RELATED QUESTIONS
What is gamma decay?
Describe alpha, beta and gamma decays and write down the formulae for the energies generated in each of these decays.
Complete the following equation describing nuclear decay.
\[\ce{_8^19O->e^- { +}}\] _____
Complete the following equation describing nuclear decay.
\[\ce{_90^228Th->\alpha { +}}\] _____
Complete the following equation describing nuclear decay.
\[\ce{_7^12N -> _6^12C {+}}\] ______
Derive the relationship between half-life and decay constant of a radioelement.
The half-life of 67Ga is 78 h. How long will it take to decay 12% of the sample of Ga?
0.5 g sample of 201Tl decays to 0.0788 g in 8 days. What is its half-life?
65% of 111In sample decays in 4.2 d. What is its half-life?
A 3/4 of the original amount of radioisotope decays in 60 minutes. What is its half-life?
A sample of 32P initially shows activity of one Curie. After 303 days, the activity falls to 1.5 × 104 dps. What is the half-life of 32P?
In Hydrogen, the electron jumps from the fourth orbit to the second orbit. The wavenumber of the radiations emitted by an electron is ______
The decay constant λ of a certain radioactive material is 0.2166 per day. The average life τ of the radioactive material is ______
Show that half life period of radioactive material varies inversely to decay constant λ.
The rate of radioactive disintegration at an instant for a radioactive sample of half-life 2.2 x 109 s is 1010 s-1. The number of radioactive atoms in that sample at that instant is, ______
A radioactive substance has half life of 3 hours. 75 % of the substance would decay in ____________.
For radioactive substances, the fraction of its initial quantity (N0) which will disintegrate in its average lifetime is about ______.
(e = 2.71)
The activity of a radioactive substance decreases by a factor of 32 in one hour. The half-life of the substance (in min) is ______.
The graph obtained by plotting loge (A) [A is the activity of a radioactive sample] against t (time) out of the following is:
The disintegration rate of a radio-active sample is 1010 per hour at 20 hours from the start. It reduces to 5 × 109 per hour after 30 hours. Calculate the decay constant.
Show that the number of nuclei of a radioactive material decreases exponentially with time.
The half-life of \[\ce{^238_92U}\] undergoing ∝- -decay is 4.5 × 109 years. What is the activity of 1g sample of \[\ce{^238_92U}\]?
Define half-life period.
In one mean lifetime of a radioactive element the fraction of the nuclei that has disintegrated is ______. [e is the base of natural logarithm]
