Question

What is the wavelength of a 4000- eV (4.0- keV ) X-ray?

Express your answer to two significant figures and include the appropriate units.

Answer 1

E = 4000 eV x (1.6 x 10^-19 J) = (6.4 x 10^-16 J)
λ = h x c / E = (6.62 x 10^-34 J.s) x (3 x 10^8 m/s) / (6.4 x 10^-16 J)
λ = 3.10 x 10^-10 m -> (1 nm = 10^-9 m)
λ = 0.31 nm