Chapter 30, Problem 49P

(a)

To determine

An expression for the critical density of the universe in the number of H atoms per cubic meter assuming that the whole universe is only hydrogen.

(b)

To determine

The average number of atoms in a room of dimension $4\text{m}\times 7\text{m}\times 3\text{m}$.

(c)

To determine

Compare the number of atoms calculated in section (b) with the practical number of atoms generally found in a room.