Consider aiming a beam of free electrons towards free protons. When they scatter, an electron and a proton cannot combine to produce a H-atom,

(a) Because of energy conservation
(b) Without simultaneously releasing energy in the form of radiation
(c) Because of momentum conservation
(d) Because of angular momentum conservation

1. (b, c)

2. (a, d)

3. (a, b)

4. (c, d)

(3) Hint: The energy of H-atom is larger as compared to the energy of free electrons.
When beam of free electrons is aiming towards free protons, then, they scatter but an electron and a proton cannot combine to produce a H-atom because of energy conservation and without simultaneously releasing energy in the form of radiation.