The number of de Broglie waves associated with the electron in its \( n \)-th orbit is given by: \[ n = \frac{2 \pi r}{\lambda} \] where \( r \) is the radius of the orbit and \( \lambda \) is the de Broglie wavelength of the electron. For the third orbit (\( n = 3 \)), we have 3 complete de Broglie waves.
Hence, the correct answer is (B).
For the reaction:
\[ 2A + B \rightarrow 2C + D \]
The following kinetic data were obtained for three different experiments performed at the same temperature:
\[ \begin{array}{|c|c|c|c|} \hline \text{Experiment} & [A]_0 \, (\text{M}) & [B]_0 \, (\text{M}) & \text{Initial rate} \, (\text{M/s}) \\ \hline I & 0.10 & 0.10 & 0.10 \\ II & 0.20 & 0.10 & 0.40 \\ III & 0.20 & 0.20 & 0.40 \\ \hline \end{array} \]
The total order and order in [B] for the reaction are respectively: