What is the wavelength, in nm, of radiation with an energy of 2.668 x 10^ (-19) J

V=E/h

v is the frequency

h is the planks constant which is 6.626 x10^-34

v is therefore [2.668 x 10^-19] / 6.626 x10^-34=4.027 x10^14

c (speed of light) = wavelength x frequency

c is always = 3.0 x10^8

therefore wavelength = (3.08 x10^8) / 4.027 x 10^14=7.649 x10^-7

convert to nm

= (7.649 x10^-7) x (1.0 x 10 ^9 nm) = 764nm