Question

While high energy beam interact with atoms why only inner shell electrons are emitted? why not outer shell electrons..?

Answer 1

The answer lies in Neil Bohr’s second postulate: i.e whenever transition of an electron occurs from one energy level (say W2) to another energy level (W1) it results in emission of radiation. That is given by
F=W2-W1/h
(w1,w2 are different energy levels of different shells in an atom)
Here f = frequency of radiation / W1,W2 are energy levels / H = plancks constant
And conversely If we want to excite an electron from energy state W1 to W2 we must provide the wave with the energy level of ‘hf’ = W2-W1. Here the fact is that the electron excitation doesn’t happened with every energy level beams but it should meet the condition that product of planks constant and frequency should be equal to the discrete energy levels existing in the atom. As per this statement we can understand that to excite an electron in higher energy level (that is nearer to nucleus) we should provide higher energy beam (or higher energy beam can support excitation of electron nearer to the nucleus)