The mean lives of a radioactive substance are 1620 years and 405 years for α -emission and β-emission respectively. The time during which three fourth of a sample will decay if it is decaying both by α -emission and β-emission simultaneously.

see full answer

Talk to JEE/NEET 2025 Toppers - Learn What Actually Works!

Real Strategies. Real People. Real Success Stories - Just 1 call away

An Intiative by Sri Chaitanya

449 years

349 years

249 years

149 years

answer is A.

(Unlock A.I Detailed Solution for FREE)

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Detailed Solution

Total decay constant is λ=1τ1+1τ2=11620+1405=1324sec-1 t=1λln4=324×ln4=449 yr

Watch 3-min video & get full concept clarity