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The half life of radioactive isotope ‘X’ is 50 years. It decays to another element ‘Y’ which is stable. The two elements ‘X’ and ‘Y’ were found to be in the ratio of 1 : 15 in a sample of a given rock. The age of the rock was estimated to be
Options
(a) 150 years
(b) 200 years
(c) 250 years
(d) 100 years
Correct Answer:
200 years
Explanation:
Let no. of atoms in X = Nₛ, No. of atoms in Y = Nₜ
By eq. Nₛ / Nₜ = 1/15
Part of Nₛ = 1/16 (Nₛ + Nₜ) = 1/2⁴ (Nₛ + Nₜ)
So, total 4 half lives are passed, so, age of rock is 4 x 50 = 200 years.
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Topics: Radioactivity
(83)
Subject: Physics
(2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
- The potential energy of a long spring when stretched by 2 cm is U.
- A ball rolls off the top of stair way with a horizontal velocity of magnitude 1.8 m/s
- A long solenoid has 500 turns. When a current of 2 ampere is passed through it
- The density of ice is 0.9 g/cc and that of sea water is 1.1 g/cc
- The identical loops of copper and aluminium are moving with the same speed
Topics: Radioactivity (83)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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