Units and Measurements question for JEE Main (JEE Main 2024 (8 Apr, Shift 1)), with solution

Answer: (B) $b$ is order of magnitude for $a \le 5$

When a number is written as $a\times10^b$, the power $b$ is its order of magnitude if $a$ is not more than about 5 (strictly, $a \le \sqrt{10} \approx 3.16$ under the rounding rule). If $a > 5$, the order of magnitude becomes $b + 1$.

So $b$ is the order of magnitude for $a \le 5$.

Solution by Sreeraj P, M.Sc Physics