Which of the Following Relationships Is Not Valid as Applied $\lambda$

Which of the following relationships is not valid as applied to infrared spectroscopy?

A) "wavenumber = 1/ $\lambda$ (in cm) "
B) " $\Delta$ E = h $\upsilon$ "
C) " $\Delta$ E = $\lambda$ $\upsilon$ "
D) " $\upsilon$ = 4.12 $\surd$ (K/ $\mu$ ) "