# What is the half-life of a radioactive substance?

## What is the half-life of a radioactive substance?

half-life, in radioactivity, the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay (change spontaneously into other nuclear species by emitting particles and energy), or, equivalently, the time interval required for the number of disintegrations per second of a radioactive …

### How do you calculate half-life decay?

How to calculate half life? To find half-life: Find the substance’s decay constant. Divide ln 2 by the decay constant of the substance.

How do you calculate half-life examples?

The time taken for half of the original population of radioactive atoms to decay is called the half-life. This relationship between half-life, the time period, t1/2, and the decay constant λ is given by t12=0.693λ t 1 2 = 0.693 λ .

Why is half-life called half-life?

The name Half-Life was chosen because it was evocative of the theme, not clichéd, and had a corresponding visual symbol: the Greek letter λ (lower-case lambda), which represents the decay constant in the half-life equation.

## What is the half-life for uranium 235?

The half-life of uranium-238 is about 4.5 billion years, uranium-235 about 700 million years, and uranium-234 about 25 thousand years.

### How many half lives have passed?

10.3: Half-Life

Number of Half-Lives Passed Fraction Remaining Percentage Remaining
1 1/2 50
2 1/4 25
3 1/8 12.5
4 1/16 6.25

How do you find half-life without a calculator?

One quick way to do this would be to figure out how many half-lives we have in the time given. 6 days/2 days = 3 half lives 100/2 = 50 (1 half life) 50/2 = 25 (2 half lives) 25/2 = 12.5 (3 half lives) So 12.5g of the isotope would remain after 6 days.

How do you calculate a drugs half-life?

1. Half life. The half-life of a drug is is the period of time required for its concentration or amount in the body to be reduced by exactly one-half.
2. Example 2. Drug B has a half-life of 3 hours.
3. 6hr = 2 half − life = 1800 ÷ 2 = 900 / 9hr = 3 half − life = 900 ÷ 2 = 450 /
4. 40 − 32 = 8ℎ = 480

## What are 3 sources of radiation?

Natural background radiation comes from the following three sources: