Answer:
Photon
Step-by-step explanation:
The photon is the quantum of light. From a classifical point of view, ligth is a wave (an electromagnetic wave), but it also acts as made by particles (quanta of energy) called photons, and this behaviour is described by quantum mechanics.
When an atom changes from a higher energy level to a lower energy level, energy is released in the transition. This energy is carried away by a single photon of light. More specifically, the photon carries an energy which is equal to the difference in energy between the two levels of the atom:
![\Delta E=E_1 - E_2](https://img.qammunity.org/2020/formulas/physics/high-school/va0cv60b48haltm4usmq3wr2yfhcnuzyzp.png)
And the frequency of the photon will depend on its energy, according to the equation
![E=hf](https://img.qammunity.org/2020/formulas/physics/middle-school/9uzgkt469myysjhcl9aq934zilrqvjwu1y.png)
where
E is the photon's energy
h is the Planck constant
f is the photon's frequency