Chapter 17, Problem 72A

To determine

The number of atoms in typical baby’s hair

Answer to Problem 72A

The number of atoms present in typical baby's hair is $100000$ .

Explanation of Solution

Given:

The diameter of typical atom is,

  $d=2\times {10}^{-10}\text{m}$

The thickness of baby's hair is,

  $t=2\times {10}^{-5}\text{m}$

Formula used:

Let $n$ be the number of atoms present in thickness $t$ . Then the relation between thickness of hair and diameter of atom is,

  $t=nd$

  $n=\frac{t}{d}$

Calculation:

Substitute $2\times {10}^{-5}\text{m}$ for $t$ and $2\times {10}^{-10}\text{m}$ for $d$ .

  $n=\frac{2\times {10}^{-5}\text{m}}{2\times {10}^{-10}\text{m}}$

  $=100000$

Conclusion:

Therefore, the number of atoms present in typical baby's hair is $100000$ .