What is the longest wavelength λ of light that will provide photons of sufficient energy to break the π bond and cause the isomerization? express your answer numerically in nanometers?

Ans: The longest wavelength = 450nm(Approx)

Explanation:

Since,

λ=hc/E --- (1)

where h=Plank's Constant=6.626x10^-34 Js

and c=Speed of Light = 3 x10^8 m/s

The energy to break a π bond =E= 4.42*10^-19 J/molecule

Substitute those values into equation (1):
λ=(6.626 x 10^-34)(3 x 10^8)/(4.42*10^-19)
λ=4.497*10^-7m 

or(in nm)

λ=450nm(approx)

less than one you can't create energy

an electric circuit