Answer:
The light radiated from the Sun's surface reaches Earth in about 8 minutes. However, the energy of this light was released by fusion in the Sun's core about several hundred thousand years ago.
Step-by-step explanation:
Nucleosynthesis is the fusion of lighter elements into heavier elements. For the Sun the main mechanism of fusion is the proton - proton chain, in which two hydrogen atoms fuse into helium, in the course of the fusion photons are created.
When those photons start their travel from the core to the surface of the star, they will interact with different atoms in the whole way (the main free path).
More precisely, when a photon¹ is absorbed by an electron in an atom of a particular element, the electron will get to a higher state. When it comes back to the ground state, a photon will be emitted again.
The process described above is repeating multiple times for every photon until they reach the Sun surface.
The whole process can take about several hundred thousand of years.
Key term:
¹Photon: Particle that constitutes light.