If the half-life of a radioactive substance is 10 days, then the time taken for 75% of the original sample to decay is:
Show answer & explanation
Correct answer: C
Explanation
Correct Answer
20 days
Explanation
Half-life is the time required for a radioactive substance to reduce to half of its original amount.
Given:
• Half-life = 10 days
A decay of 75% means that only 25% of the original substance remains.
Initially = 100%
After 10 days = 50% remains
After 20 days = 25% remains
Thus, 75% of the substance has decayed.
Therefore, the time required for 75% decay is 20 days.
Key Points
• Half-life is the time in which the quantity of a radioactive substance becomes half.
• After 10 days, 50% of the substance remains.
• After 20 days, 25% of the substance remains.
• If 25% remains, it means that 75% has decayed.
Additional Facts
• Radioactive decay is a natural and spontaneous process.
• Every radioactive element has a fixed half-life.
• The concept of half-life is widely used in nuclear physics, medicine, and archaeology.
Important Questions
Question: If the half-life of a substance is 10 days, how long will it take for 50% decay?
Answer: 10 days.
Question: If the half-life of a substance is 10 days, how long will it take for 75% decay?
Answer: 20 days.