There is a relationship between the energy of a photon and its wavelength. This can be expressed as a mathematical equation shown below:
E = hc/λ
where
h is the Planck's constant equal to 6.62607004 × 10⁻³⁴ m² kg / s
c is the speed of light equal to 3× 10⁸ m/s
λ is the wavelength
3.5×10⁻¹⁶ J = (6.62607004 × 10⁻³⁴ m² kg / s)(3× 10⁸ m/s)/λ
Solving for λ,
λ = 56.8×10⁻⁹ m or 56.8 nm
