Step 1: The energy of a photon is related to its wavelength by the equation:
\[
E = \dfrac{hc}{\lambda},
\]
where \( h \) is Planck’s constant and \( c \) is the speed of light.
Step 2: Since energy and wavelength are inversely proportional, the relation between the wavelengths is:
\[
\lambda_1 = \frac{1}{2} \lambda_2.
\]
Final Answer:
\[
\boxed{\lambda_1 = \frac{1}{2} \lambda_2}
\]