The energy of a photon is 3×10−12 ergs . What is its wavelength in nm? (h=6.62×10−27 erg.sec;C=3×1010Cms−1)

E=3×10−12 ergs       λ=? nm E=hcλ ⇒λ=hcE                            =6.6×10−27×3×10103×10−12cm                           =6.6×10−5 cm                                                   =6.6×10−5×107 nm(∵ 1 cm=107nm)                           =660 nm