Step 1: Understanding the Concept
A photon emitted in a transition has energy equal to the difference between the two levels, \(\Delta E=\dfrac{hc}{\lambda}\).
Step 2: Energy gaps
From \(2E\) to \(E\), the gap is \(E\), so \(\lambda=\dfrac{hc}{E}\).
From \(\dfrac{4E}{3}\) to \(E\), the gap is \(\dfrac{E}{3}\).
Step 3: Calculation
\(\lambda'=\dfrac{hc}{E/3}=3\,\dfrac{hc}{E}=3\lambda\).
Final Answer:
The wavelength of the second photon is 3 times lambda, which is option (A).
\[ \boxed{\text{(A) }3\lambda} \]