197- If in the hydrogen atom the electron transitions from $n = 2$ to $n = 4$, its speed becomes how many times? (1) $2$ (2) $4$ (3) $\sqrt{2}$ (4) $\dfrac{1}{2}$
\textbf{197-} If in the hydrogen atom the electron transitions from $n = 2$ to $n = 4$, its speed becomes how many times?
\hspace{1cm} (1) $2$ \hspace{2cm} (2) $4$ \hspace{2cm} (3) $\sqrt{2}$ \hspace{2cm} (4) $\dfrac{1}{2}$