a vacancy created when an electron leaves a covalent bond.
3.
absence of free electrons.
4.
an artificially created particle.
(b) Hint: The hole is created by the absence of electrons.
The concept of hole describes the lack of an electron at a position where one could exist in an atom or atomic lattice. If an electron is excited into a higher state, it leaves a hole in its old state.
Thus, the hole can be defined as a vacancy created when an electron leaves a covalent bond.