Final Answer:
The part of the sun that is actually visible with the human eye is the photosphere. Thus, the correct answer is option 1) photosphere.
Step-by-step explanation:
The photosphere is the outermost layer of the sun that release light and heat, making it the only visible layer to the eye. This layer has a temperature of approximately 5,500 degrees Celsius. The photosphere is responsible for the sunlight that reaches Earth and allows us to see the sun as a bright, glowing disc in the sky.
When we observe the sun, what we see is the light emitted from the photosphere. The other layers of the sun, such as the corona and chromosphere, are not visible to the eye from Earth's surface. The corona, for instance, is visible during a solar eclipse or with specialized instruments due to its much lower temperature compared to the photosphere. The chromosphere, lying just above the photosphere, is also usually obscured by the brightness of the photosphere but becomes visible briefly during a solar eclipse. Therefore, the correct answer is option 1) photosphere.