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)
