Find the photon energy in (i) calories (ii) watt hour (iii) electron volt, for e.m. wave of wavelength `300 mu m`. Give, `h=6.6xx10^-34Js.`

Answer

(i) `1.6xx10^(-22) cal. (ii) 1.83xx10^(-25)Wh (iii) 4.125xx10^-3eV`

Explanation

`lambda=300 mum=300xx10^-6m=3xx10^-4m`,
`E=(hc)/lambda=(6.6xx10^(-34)xx3xx10^8)/(300xx10^-6)`
`=6.6xx10^(-22)J`
`=(6.6xx10^(-22))/4.2 cal=(6.6xx10^(-22))/(60xx60)` watt hour
`=(6.6xx10^(-22))/(1.6xx10^(-19))` electron-volt.