How interesting that you described it as a "fall" to a
"lower energy" level. You picked up that description
from hearing it used somewhere before.
It's an accurate description, and it's a big hint to the answer.
When an object falls from a higher to a lower place,
it gives up gravitational potential energy, and then
it has less of it. If it wants to return to the height
where it was before, somebody has to come along
and do work on it to lift it, and give it back the energy
it needs to be up at that height.
Same with your electron. The farther it is from the
nucleus, the more potential energy it has ... only
it's electrical, not gravitational.
If the electron emits (gives out) some energy, then it
"falls" to a lower orbit / lower energy level.
Then, If somebody comes along and gives it
more energy, it can rise to a higher orbit / higher
energy level.
And if they give it enough energy, then it can
escape from the atom all together !
