What is the widest area in the sun's atmosphere? What is the thickest?

The photosphere is located outside the troposphere and belongs to the lowest or innermost layer of the solar atmosphere. The surface of the photosphere is gaseous, with an average density of only several hundred million times that of water and a thickness of 500 kilometers, so the photosphere is opaque.

The atmosphere near the photosphere is called chromosphere, which is not easy to be observed at ordinary times. In the past, this area was only visible during a total solar eclipse. When the moon hides the bright brilliance of the ball of light, people can find that there is a rosy brilliance on the edge of sun gear, that is, the ball of color. Chromosphere is about 8,000 kilometers thick, and its chemical composition is basically the same as that of the photosphere, but the density and pressure of matter in chromosphere are much lower than that of the photosphere.

The corona is the outermost layer of the solar atmosphere. The material in the corona is also plasma, the density is lower than that of chromosphere, and the temperature is higher than that of chromosphere, reaching several million degrees Celsius. During the total solar eclipse, very bright silvery white light can be seen around the surface of the sun, which is the corona. The corona extends over the chromosphere and extends to several solar radii. The corona will also expand outward, and thermoelectric gas particles will continue to flow out of the sun, forming a solar wind.

I hope my answer can help you!