Find the energy of a photon of wavelength `4950 Å` in eV (`h = 6.62 xx 10^(-27)` erg.s) . What is the momentum of this photon?

Explanation

`lamda = 4950 Å xx 4950 xx 10^(-8) cm`
Hence energy of a photon,
`E = hf = (hc)/(lamda) = (6.62 xx 10^(-27) xx 3 xx 10^(10))/(4950 xx 10^(-8))`
`= 4.012 xx 10^(-12)` erg
`= (4.012 xx 10^(-12))/(1.6 xx 10^(-12)) = 2.5 eV`
Momentum of photon,
`p = (E)/(c) = (4.012 xx 10^(-12))/(3 xx 10^(10))`
`= 1.34 xx 10^(-22) "dyn.s"`