An Atom in Its Ground State Absorbs a Single Photon

Multiple Choice

An atom in its ground state absorbs a single photon of light and then relaxes back to the ground state by emitting an infrared photon (1,200 nm) followed by an orange photon (600 nm) . What is the wavelength of the photon that was absorbed initially?

A) 600 nm
B) 1,200 nm
C) 1,800 nm
D) 900 nm
E) 400 nm