[joyb]

"The pigment in a carrot is carotene which is a chromophore consisting of 11 conjugated double bonds. Assume the electrons are free to move along the whole chain (effectively a 1-D box) and calculate the energy of the first transition. The average C-C=C repeating unit length is 0.144nm and there will be 2 electrons
present from each unit."

I've been trying to do this using the equations  E=n²h²/8mL² and E=hc/λ, taking excited n as 2,  initial n as 1, m as 9.11x10^-31 and L as 0.144x11x10^-9, but I can't seem to get a wavelength in the visible spectrum. What am I doing wrong?