Answer
310 nm
Work Step by Step
Recall the equation E= hν = hc/λ
Then, wavelength, λ= hc/E
Here, H is the Planck's constant, c is the speed of light and E is the energy.
Substituting the values:
λ=$\frac{(6.626×10^{-34}Js)(3.00×10^{8}m/s)}{6.4×10^{-19}J}$=$ 3.1×10^{-7}m$= 310 nm
