The reason it takes significantly longer for light to travel from the core of the Sun to its surface compared to the time it takes to reach the Earth's surface is primarily due to the difference in density and opacity of the two mediums.
Inside the Sun, the core is a region where nuclear fusion occurs, converting hydrogen into helium and releasing an enormous amount of energy. The core is extremely hot and dense, with photons (particles of light) constantly being generated through these nuclear reactions. However, the Sun's core is so dense that photons cannot travel far before being absorbed and re-emitted by other particles in the plasma. This process of absorption and re-emission significantly slows down the progress of the photons toward the surface.
On the other hand, the outer layers of the Sun, such as the radiative zone and the convective zone, are less dense and allow photons to travel relatively freely. These layers are not as optically thick, so the photons can scatter and make their way toward the surface with less obstruction.
In contrast, the Earth's atmosphere, though composed of gas, is relatively transparent to visible light. As a result, when light from the Sun reaches the outermost layers of the Sun's atmosphere (called the photosphere), it can easily pass through the vacuum of space and travel through the atmosphere to reach the surface of the Earth without significant absorption or scattering.
The difference in opacity and density between the Sun's core and the Earth's atmosphere accounts for the substantial difference in the time it takes for light to traverse these distances. The light generated in the core of the Sun must travel through a much more opaque and dense medium, causing a significant delay before it reaches the surface.