The energy of an electromagnetic radiation is 19.875×10−13 ergs . What is the wave number in cm−1 ?(h=6.625×10−27erg.sec;c=3×1010cm.sec−1)

E=19.875×10−13 ergs             ϑ¯=? cm−1 E=hcϑ¯⇒ϑ¯=Ehc                            =19.875×10−136.6×10−27×3×1010 cm−1                             =104                             =10,000 cm−1