Question

The number of de Broglie waves of an electron in the $n^{th}$ orbit of an atom is :

• A. $n$
• B. $n-1$
• C. $n+1$
• D. $2n$

Answer 1

The correct option is A $n$

The only places an electron can take in an atom are those where it can complete a multiple of a full wavelength. So when an electron (in wave form) starts from a certain point it must come back to the same point and be at the exact same position as when it started from that point. Otherwise, the wave wouldn't coincide with itself, and it would consequently interfere with itself and possibly destroy itself. This can't happen according to the laws of the conservation of matter and energy, so the electron only takes the orbits in which it can complete a number of full wavelengths. The number of waves is thus $n$.