Question

What is the wavelength of an 0.12- eV infrared photon?

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

Answer 1

E = (h x c) / λ
0.12 eV = (6.626 x 10^-34 J.s) x (3 x 10^8 m/s) / λ
0.12 x (1.6 x 10^-19) J = 1.9878 x 10^-25 / λ
(1.92 x 10^-20) x λ = 1.9878 x 10^-25
λ = (1.9878 x 10^-25) / (1.92 x 10^-20)
λ = 1.0353125 x 10^-5
(1 nm = 10^-9 m)
λ = 1.0 x 10^4 nm