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A mixture consists of two radioactive materials A₁ and A₂ with half lives of 20s and 10s respectively. Initially the mixture has 40 g of A₁ and 160 g of A₂. The amount of the two in the mixture will become equal after:
Options
(a) 60 s
(b) 80 s
(c) 20 s
(d) 40 s
Correct Answer:
40 s
Explanation:
Let, the amount of the two in the mixture will become equal after t years.
The amount of A₁, which remains after t years N₁ = N₀₁ / (2)ᵗ/²⁰
The amount of A₂, which remains after t years N₂ = N₀₂ / (2)ᵗ/¹⁰
According to the problem N₁ = N₂
40 / (2)ᵗ/²⁰ = 160 / (2)ᵗ/¹⁰ ⇒ 2ᵗ/²⁰ = 2(ᵗ/¹⁰⁻²)
t/20 = t/10 – 2 ⇒ t/20 – t/10 = 2
t/20 = 2 ⇒ t = 40 s
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Topics: Radioactivity
(83)
Subject: Physics
(2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
- In a parallel plate capacitor of capacitance C, a metal sheet is inserted
- Two concentric spheres kept in air have radii R and r.
- A wire of length 1 m is placed in a uniform magnetic field of 1.5 tesla at an angle
- Force required to move a mass of 1kg at rest on a horizontal rough plane
- The root mean square speed of oxygen molecule (O₂) at a certain temperature is v.
Topics: Radioactivity (83)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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