Which of the Following Photons Has the Lowest Frequency?
A) $\lambda$

Which of the following photons has the lowest frequency?

A) a photon from a Nd:YAG laser with $\lambda$ = 1,064 nm
B) a photon from an Ar⁺ laser with $\lambda$ = 514.5 nm
C) a photon from a Kr⁺ laser with $\lambda$ = 647 nm
D) a photon from an ArF laser with $\lambda$ = 193 nm
E) a photon from a He-Ne laser with $\lambda$ = 633 nm