# Homework Help: Quantum mech help - radii of some atoms

1. Dec 28, 2004

### yxgao

What is the ratio of the radii of muonic hydrogen to hydrogen? Muonic hydrogen consists of a proton and $$\mu^{-}$$. How do you calculate this??

2. Dec 28, 2004

### dextercioby

The concept of Radius of an atom is itself entirely classical,so when reading the text of the problem u should have pictured Bohr's semiclassical model for finite mass nucleus.
U'll be neding this formula
$$R_{n}=\frac{1}{Z}\frac{4\pi\epsilon_{0}\hbar^{2}}{\mu e^{2}} n^{2}$$
,where
$$\frac{1}{\mu}=\frac{1}{m_{nucleus}}+\frac{1}{m_{electron/muon}}$$

Daniel.