So, the equation that we will use to solve this problem is as follows:
E = hc / lambda where:
E is the required energy
h is Planck's constant = 6.626 × 10^-34 J∙s
c is the speed of light = 3 x 10^8 m / sec
lambda is the wavelength = 12.9 cm
Substituting with these values in the above equation, we can calculate the energy as follows:
E = (6.626 × 10^-34 x 3 x 10^8) / (12.9 x 10^-2) = 1.54 x 10^-24 Joules
