The correct answer is quantum.
Quantum is the smallest is the smallest quantity of energy that can be emitted or absorbed .This can be absorbed or emitted in the form of electromagnetic radiation. The energy of single quantum can be given by the equation:
E=hν where E= energy absorbed or emitted
h=plank's constant 6.63 x 10⁻³⁴ Js,
ν= frequency of radiation.
