Why is the electron in an atom restricted to revolve around the nucleus at certain fixed distances ?

The sub atomic particles that revolve around the nucleus

According to Bohr's model of an atom, the electrons revolve round the nucleus in

How many times the normal electrons of hydrogen atom revolve round the nucleus in on sec ?

How many time the normal electrons of hydrogen atom revolve round the nucleus in one sec? velocity of the electron

The probability of finding the electron in the space around the nucleus is given by-

alpha - particles scattering experiment confirms i) Nucleus is positively charged. ii) Nucleus contains electrons. iii) Electrons revolve around the nucleus. iv) Most of the space inside the atom is empty.

Why don't you get an image for certain object distances ?