Loading...
UPSC 2001: A radioactive substance has a half-life of four months. Three fourth of the substance would decay in
(a)3 months
(b)4 months
(c)8 months
(d)12 months
Attempt This Question
Not attemptedCorrect Answer: (c) 8 months
Each half-life leaves 50 % of the original nuclei undecayed. After two half-lives, (½)² = ¼ remains, meaning ¾—or 75 %—has decayed. Two half-lives equal 2 × 4 months = 8 months, hence option (c). ([physics.stackexchange.com](https://physics.stackexchange.com/questions/630624/calculating-radioactive-decay?utm_source=openai))
Related UPSC Questions
More from Energy & Environment
2004easy
Match List I (Fuel Gases) with List II (Major Constituents) and select the correct answer using the codes given below: List I (A) CNG (B) Coal gas (C)
1997easy
Which one of the following has the highest fuel value?
2005easy
Assertion (A): The main constituent of the Liquefied Petroleum Gas is methane. Reason (R): Methane can be used directly for burning in homes and facto
Frequently Asked Questions
What is the correct answer to this UPSC 2001 Science & Technology question?▼
The correct answer is option (c): 8 months. Watch the detailed video explanation in our Sherlocking Prelims course on UnlockIAS.
Which year was this Energy & Environment question asked in UPSC Prelims?▼
This question was asked in UPSC CSE Prelims 2001, GS Paper 1, as Question 113. It falls under Science & Technology > Energy & Environment.
What is the difficulty level of this UPSC question?▼
This question is rated "easy". It tests basic recall and most well-prepared aspirants should answer it correctly.
How many UPSC Prelims questions have been asked from Energy & Environment?▼
UPSC has asked 48 questions from Energy & Environment (under Science & Technology) across multiple years. Visit the topic page to see the full list and year-wise trends.