When an electron falls from a higher energy to a lower energy level, the difference in the energies appears in the form of electromagnetic radiation. Why cannot it be emitted as other forms of energy ?

Explanation

Because such electron comes in an orbit, closer to nucleus, its speed gets increased. i.e., it gets accelerated.
Here electron (which is a charged particle) performs an accelerated motion, during which energy associated with periodically oscillating electric and magnetic fields, gets emitted in the form of radiation.