electromagnetic radiation - How do light waves get their size?

An atom or (small) molecule has the size of about 100pm. Elektromagnetic waves range from about 0.1nm up to 1 km. The most common way waves (like light) are caused by 'jumping' electrons to another orbit, so their 'jump' is probably smaller than 100pm.

But how do they succeed in creating waves with a length of 700nm, about a 1000 times larger than the 'jump' they make?