Question

The surface of the Sun appears sharp in visible light because:

(a) the photosphere is cooler than the layers below it
(b) the photosphere is thin compared to the other layers in the Sun
(c) the photosphere is less dense than the convection zone
(d) the sun has a distinct surface

Answer 1

The Sun's photosphere appears sharp in visible light because it's the layer where the solar atmosphere transitions from transparent to opaque over a short distance, giving the illusion of a well-defined surface.

Step-by-step explanation:

The surface of the Sun, known as the photosphere, appears sharp in visible light because this layer is where the Sun becomes opaque, marking the boundary past which we cannot see. The photosphere looks sharp only from a distance, similar to how a cloud might appear to have a distinct edge from afar, even though there is no sudden change when passing through a cloud. The sharp appearance of the photosphere is due to the rapid transition from transparent to opaque that occurs in a comparatively thin layer around 400 kilometers thick. Astronomers have found that this solar atmosphere changes from almost perfectly transparent to almost completely opaque in that short distance, much like how the Earth's atmosphere can become opaque on a smoggy day.