# NEET Physics Nuclei Questions Solved

At any instant the ratio of the amount of radioactive substances is 2 : 1. If their half lives be respectively 12 and 16 hours, then after two days, what will be the ratio of the substances
(a) 1 : 1                 (b) 2 : 1
(c) 1 : 2                 (d) 1 : 4

(a) Number of half lives in two days four substance 1 and 2 respectively are ${\mathrm{n}}_{1}=\frac{2×24}{12}=4$ and  ${\mathrm{n}}_{2}=\frac{2×24}{1.6}=3$
By using $\mathrm{N}={\mathrm{N}}_{0}{\left(\frac{1}{2}\right)}^{\mathrm{n}}⇒\frac{{\mathrm{N}}_{1}}{{\mathrm{N}}_{2}}=\frac{{\left({\mathrm{N}}_{0}\right)}_{1}}{{\left({\mathrm{N}}_{0}\right)}_{2}}×\frac{{\left(\frac{1}{2}\right)}^{{\mathrm{n}}_{1}}}{{\left(\frac{1}{2}\right)}^{{\mathrm{n}}_{2}}}$

$=\frac{2}{1}×\frac{{\left(\frac{1}{2}\right)}^{4}}{{\left(\frac{1}{2}\right)}^{3}}=\frac{1}{1}$

Difficulty Level:

• 39%
• 20%
• 20%
• 24%
Crack NEET with Online Course - Free Trial (Offer Valid Till August 26, 2019)