Half-life Definition and 133 Threads

This being a physics forum, I'm sure many of you have heard of the 1998 computer game Half-Life. If you don't know, the game is set within a top secret research laboratory deep within the deserts and mesas of Arizona. All hell breaks loose after a massive screwed-up experiment. The...

Homework Statement After 25 years, 60% of a radioactive material decays. What is the half-life? Homework Equations I used a ratio of 25/.60= x/.50 The Attempt at a Solution I also tried this ratio as 25/.40= x/.50 I am not really sure what equation I should be using but this...

Question: Carbon-14 has a half-life of 5730 years. A bone is found in which \frac{7}{8} of the original [16g of] carbon-14 has decayed. How old is the bone? Formula: C(t)=Co(\frac{1}{2})\frac{t}{H} (it's hard to see but it says \frac{1}{2} to the power of \frac{t}{H}) C(t) - the number at...

Would the observed half-life of a sample of a radioactive isotope (eg. iodine 131) be different from the nominal half-life when it is cooled down to a temperature near absolute zero. Have there been any experiments conducted to examine this question?

Homework Statement Problem 1 – Krane 8.7] (a) compute the Q values for the decays 224Ra → 212Pb + 12C and 224Ra → 210Pb + 14C. (b) Estimate the half-lives for these two possible decay processes. 224Ra is a α emitter with a half-life of 3.66 days. Homework Equations I am assuming that...

Homework Statement I have conducted an experiment and found the gradient λ of a graph to be (2.15x10^-4) +- (0.15x10^-4) The graph being ln(A) i.e. the number of disintegrations/unit time - dN/dt against time t The half-life is T(1/2) = ln(2)/λ = -3223.9 How do I find the...

This link is confusing me. http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html In this link, with non-relativistic method, half life is calculated as 21.8. But with relativistic method half life is calculated as 4.36. We calculate half life considering time dilation for muon...

Hey guys, I've been given a worksheet with a couple of questions concerning radioactivity, half-life etc. It is high school level and for me, it seems like the first year doing physics as our current teacher is the first one who really knows something about the subject. :) So please be patient...

Homework Statement magine performing a counting experiment for 10 minutes, counting with a detector over 30 second intervals to determine the half-life of a radioactive sample. You obtain the data given in table 1. By approximating the activity at time ti, A(ti) by the counts measured over a...

Homework Statement The polonium isotope 210Po, an alpha emitter, has a half-life of 138.38 days. You happen to have a 1.5 g cube of 210Po, so you decide to use it to boil water for tea. You fill a well-insulated container with 120 mL of water at 18° C and drop in the cube of polonium. (a)...

Homework Statement When iodine is ingested by humans they eliminate it such that on half of the body's iodine content is execreted every 4.0 days. Radioactive 131I with a physical half-life of 8.1 days is administered to a patient. When will only 1% of the isotope remain in the patient's body...

A second- order reaction of the type A + B -->P was carried out in a solution that was initially 0.075 mol dm^-3 in A and 0.050 mol dm^-3 in B. After 1.0 h the concentration of A had fallen to 0.020 mol dm^-3. a) Calculate the Rate constant. b) Solve for the half- life of each of the reactants...

Hello, I am curious. Eventhough, the half-time of an element is always the same. Why not we can't find quarter of elements vanish time, because; half life is directly proportional, 10gr 10 min -> 5gr 20min. if 10 gr vanishes in 10 min, 2.5gr vanishes in 2.5 min for 20gr radioactive material.

I apologize for the simplicity of this question in relation to the others on this site. But I've been curious, and haven't been able to find an answer. In Radioactive Dating, how do scientists know how much of a certain isotope (ie. Carbon-14, Potassium-40) was there to start with in an...

Homework Statement The spontaneous fission rate for U-238 is roughly 1 fission per gram per 100 seconds. Show that this rate is the equivalent to a half-life for spontaneous fission of ~5.5x1015 years Homework Equations none that I can find in my book The Attempt at a Solution I'm...

2.3 \cdot 10^{10} atoms decay via alpha emission have a half-life of 150 min. How many alpha particles are emitted between t=30 min and t=160 min? \begin{flalign*} 150 &= \frac{\ln 2}{\lambda}\\ \lambda &= 0.046 \\ \\ K &= K_{0}e^{(-\lambda)(t)}\\ &= (2.3 \cdot 10^{10})e^{(-0.046)(30)}\\...

Measurements of a certain isotope tell you that the decay rate decreases from 8339 decays/minute to 3037 decays/minute over a period of 4.50 days. What is the half-life T_1/2 of this isotope in days?I know that i have to relate the ratio of decay rates to the ratio of undecayed nuclei present at...

Homework Statement You want to do an experiment using 47Ca (half-life=4.53 days). You will need 3.25 μg of the nuclide. What mass of CaCO3 (100% enriched in 47Ca) must you order if it will take 50 hours to be delivered to you from the nuclear facility where it is prepared? Homework...

Homework Statement To determine volume of blood in a patient's body, a nuclear medicine technologist is injected a small amount of a radioactive isotope (T(1/2)= 45 min) into the patient's blood stream. The activity of this isotope is at the time of injection was ( 2.8x10^4 decays/second...

the assignment is written as follows: A parcel is attracting nervous attention at australian post. the parcel is radioactive and inspectors are trying to identify the material. Suppose they make the following measurements. There are 50 grams of the material and it's decaying at a rate of 0.25...

Homework Statement If 20% of a radioactive substance disappears in 70 days, what is its half-life? Homework Equations y = C*e^(k*t) where t is time in days k is the constant of proportionality? y is the current amount of substance The Attempt at a Solution 20% disappears, so...

Homework Statement An equilibrium ore mixture has an atomic ratio for \frac{U-235}{Pa-231} = 3.04x10^{6} Find the half-life of U-235 from the data. The known half-life for Pa-231 is 3.28x10^{4} years Homework Equations For secular equilibrium \frac{\lambda_{2} N_{2}}{\lambda_{1}...

Homework Statement c) In 420 days, the activity of a sample of polonium, Po, fell to one-eighth of its initial value. i) Calculate the half-life of polonium. Homework Equations The Attempt at a Solution if the activity fell by 1/8 then it went through 4 half liefs (1/2*4=1/8) so...

Is there any way we can decrease the half life of isotopes in nuclear waste? such as mutate to some other radionuclides that have a relatively shorter half life than the original isotopes generated by depleted fuel? Thanks

Suppose you have two similar particles that have gone through similar half life periods. They each have been reduced to practically infinitely small spheres. Within each sphere is a hollow space. They are both touching during a process in which they are constantly decaying, with two small...

Homework Statement 2.71g sample of radioactive KCl is decaying at a constant rate of 400Bq into the isotope 40K. which constitutes 1.17% of normal K. calculate the half life of this nuclide. Homework Equations we have dn/dt = n * lamda and t-1/2 = 0.693/lamda. The Attempt at a...

Hello :) I came across a question and I haven't been able to solve it so far. It would be great if maybe someone could give me a few tips. Here is the question: Measurements of the radioactivity of a certain isotope tell you that the decay rate decreases from 8305 decays per minute to...

Homework Statement The half life of carbon 14 is 5730 years long. Assume that dQ/dt = -rQ. Determine the constant rate r. The attempt at a solution dQ/dt = -rQ (Given) dQ/Q = -rdt (algebra) lnQ = -rt (integrate) -lnQ/t = r (algebra) How do I work in...

Say we have a decay of the form A e^{-a x} + B e^{-b x}. I haven't had much luck trying to calculate the half-life of such a decay (I'm not sure it's possible, analytically), i.e. solve A e^{-a x} + B e^{-b x} = \frac{A+B}{2}. However, if that's not possible, I'm wondering whether...

Homework Statement At present, the concentration of uranium 235 in naturally occurring uranium deposits is approximately 0.77%. What will the concentration be one billion years from now? Homework Equations N(t) = No e^ -(ln(2)/half-life)t The Attempt at a Solution i attempted...

Anyone with the same experience? we are going through this on the laboratory, we quiet don't know how to treat it but I want to be the first to figure it out... I know what it is but we need to solve how to make it stay on a normal radioactive rate before it goes critical (acourding to the...

Homework Statement Background info: The first order rate of nuclear decay of an isotope depends only upon the isotope, not its chemical form or temperature. The half-life for decay of carbon-14 is 5730 years. Assume that the amount of C-14 present in the atmosphere as CO2 and therefore in a...

Homework Statement In 1991, hikers found the frozen remains of a man in a glacier in the Alps, near the Austrian-Italian border. Carbon-14 analysis of tissue samples taken from the body revealed that the ratio of carbon-14 was 52.7% of what it was originally. Calculate the age of the body...

Homework Statement The half-life of an isotope of phosphorus is 14 days. If sample contains 2.9 × 10^16 decays such nuclei, determine its activity. Answer in units of Ci. Homework Equations / The Attempt at a Solution I know that one Ci is equal to 3.7*10^10 bq (or decay per second), I'm...

Homework Statement The half-life of a radioactive substance is 194 days. How many days will it take for 80% of the substance to decay? Homework Equations The Attempt at a Solution I had to make 1/2n=1/5. I did this by finding log25=n. After this, I needed to only multiply by...

Homework Statement If a patient is given a radioactive isotope which has a half-life of six days and a biological half-life of ten days, what is the effective half-life for the isotope. Homework Equations I know the formula for half-life calculations is T1/2 = 0.693/k The Attempt at...

Homework Statement k so An experiment is done to determine the half-life of a radioactive substance that emits one beta particle for each decay process. Measurements show that an average of 8.4 beta particles are emitted each second by 2.5 milligrams of the substance. The atomic weight of the...

1.Explain why if a sample has a very short half-life, then it will be more radioactive than an element that has a longer half-life, any clues anyone?

can help me with this question :S? If 70% of a radioactive substance remains after one year, find its half-life. and Strontium-90 is a radioactive isotope with a half-life of 29 years. If you begin with a sample of 800 units, how long will it take for the amount of radioactivity of the...

A scientist wishes to find the age of a sample of rock. Realising that it contains radioactive potassium, which decays to give a stable form of argon, the scientist started by making the following measurments: decay rate of the potassium in the sample = 0.16Bq mass of potassium in the sample...

Homework Statement *I'm only stuck on part c During the testing process for some pharmaceuticals, the drug is "tagged" with a radioactive material. This way researchers can determine if the pharmaceutical is going to other parts of the body than the intended target and what effect it has on...

Hey Everyone, I have a question regarding physics. Say you're given an RC circuit with two identical capictors and two identical resistors and that the two resistors are connected in parallel and the two capacitors are connected in parallel and both are used in the circuit. How can you...

Homework Statement The Half-life of a radioactive substance is 5 hours. A sample is tested and found to contain 0.48g of the substance. How much of the substance was present in the sample 20 hours before the sample was tested? Homework Equations The Attempt at a Solution i did...

I am trying to find out what the half-life of chromium picolinate is. I have just found out it has helped damage my kidneys, since I have taken it in large doses for years :redface:. Since I just found out today, and I took my last of it today, just before that, I want to know how long before...

Homework Statement You have a kilogram sample of a beta emitter and you want to establish its half-life. You measure 100 counts over the period of a day. What is the half-life and the error on the half-life? How would your answer be different if did a measurement for the same material but...

Homework Statement ½ Life and a First-Order Process ln [R]t = -(0.18 d-1 ) (30.d)= -5.5 4.0 x 10 13atom/L [R]t 4.0 x 10 13atom/L = e -5.5 = 0.0042 [R]t = 1.7 x 10 11 atom/L...

[SOLVED] Half Life Help Homework Statement The activity of a radioisotope is 3000 counts per minute at one time and 2736 counts per minute 48 hours later. What is the half-life of th radioisotope? This is where I'm completely lost.

[SOLVED] Decay equations: Given A0 & At, find half-life, lambda and N0 Homework Statement This is from Advanced Physics by Adams & Allday, spread 8.13 Question 5. The activity of a particular source falls from 5E8 Bq to 2E7 Bq in 20 minutes. a) What is the half-life and decay...

If I know that a sample of X has a half-life of 270 years how do I confirm this experimentally? What data would I have to collect? How about if the half-life of X was much shorter i.e. in terms of days?

Homework Statement A student takes a sample of 32,000 6He atoms and measures 31000 daughter nuclei 4 seconds later. What is the half-life of 6He? What is the daughter nucleus if the 6He underwent beta minus decay? Homework Equations N = (No)(0.5)^{t/halflife} The Attempt at...