The wave length of a photon is 5000 Å. Calculate its energy in electron volts.

Explanation

`lambda = 5000 `Å `= 5 xx 10^(-7) `m
The energy of a photon is given by `E = hv - (hc)/lambda`
`E=(6.625xx10^(34)xx3xx10^(8))/(5xx10^(-7)) =3.975 xx10^(-19)" J" = (3.975xx10^(-19))/(1.6xx10^(-19))=2.484` eV.