Uranium-238 forms Thorium-234 after radioactive decay and has a half-life of 4.5 × 10^9 years. How many years will it take to decay 75% of the initial amount?
Answer: 9 × 10^9 years
Explanation
To find the time it takes to decay 75% of the initial amount, we need to find the time it takes for 25% of the initial amount to remain.
Since the half-life is 4.5 × 10^9 years, after one half-life, 50% of the initial amount remains.
After two half-lives, 25% of the initial amount remains (50% of 50%).
Therefore, the time it takes to decay 75% of the initial amount is:
2 × half-life = 2 × 4.5 × 10^9 years = 9 × 10^9 years
This question appeared in
Past Papers (4 times)
Lecturer Physics Past Papers and Syllabus (1 times)
SPSC 25 Years Past Papers Subject Wise (Solved) (2 times)
SPSC Past Papers (1 times)
This question appeared in
Subjects (1 times)
EVERYDAY SCIENCE (1 times)
Related MCQs
- In a radioactive beta-minus decay reaction:
- A radioactive decay can be represented as shown. 91Pa^233 ---> 92U^233 +...... The emitted particle is a/an?
- The radioactivity due to C-14 isotope (half life 6000 years) a sample of wood from an ancient tomb was found to be nearly half of that fresh wood. The tomb is therefore about _____?
- Half-life of a radioactive substance depends upon?
- Rs. 1200 is lent out at 5% per annum simple interest for 3 years. Find the amount after 3 years.
- Ali take 1200 rupees borrow 5% interest for 3 years . Amount paid after 3 years is ____
- If a radioactive substance reduces to 1/16th of its original mass in 40 days, what is its half-life ?
- The uranium-238 decays to thorium-234 by process of ______?
- A 40gm radioactive material is placed in a chamber, having a half-life of 20 days. How much will be left after 80 days?
- I've been here for over four and a half billion years. Here 'four and a half' is?
