the elastric field of an electromagnetic wave changes with the time as
` E=K(1+cosOmegat) cosomegat`,where
` Omega=5xx10^(15)s_(-1), omegas^(-1)` and `K` is constant . This radiation is incident on a sample of hydrogen atoms initially in ground state. assume that atom absorbs light as photons. Neglecting , what will be the energy of ejected electron from hydrogen . [the ionisation energy of hydrogen a tom =`13.6eV` and
` h=2pixx6.6xx10^(-16)eV-s`]

Options

A. `0.7eV`
B. `0.9eV`
C. `1.4eV`
D. `2.9eV`

Answer

D

Explanation

The expression for elastric field can also be written as `E=Kcosomegat+1/2Kcos(omega-Omega)t+1/2Kcos(omega+Omega)t`. The three terms correspond to photons of energies `(homega)/(2pi),h(omega-Omega)/(2pi)`and` h(omega+Omega)/(2pi)`. The last exceeds the ionisation energy by `2.9eV`. the difference equals to the `KE` of ejected electrons.