Answer
The minimum amount of energy required to change from one isomer to another is $2.0~eV$
Work Step by Step
We can find the energy of a photon with a wavelength of $630~nm$:
$E = \frac{hc}{\lambda}$
$E = \frac{(6.626\times 10^{-34}~J~s)(3.0\times 10^8~m/s)}{630\times 10^{-9}~m}$
$E = (3.16\times 10^{-19}~J)(\frac{1~eV}{1.6\times 10^{-19}~J})$
$E = 2.0~eV$
The minimum amount of energy required to change from one isomer to another is $2.0~eV$
