Final answer:
The mottled appearance of the solar surface caused by convective movements of gas is known as granulation. Granules are the bright, hot areas that rise, spread out, cool, and then sink, creating a pattern visible in high-resolution telescope images.
Step-by-step explanation:
The mottled appearance of the solar surface is caused by a process known as granulation. Granulation occurs due to convective motions within the Sun's photosphere, where hotter and brighter gas rises and cooler, darker gas sinks. The brighter areas are known as granules, which are columns of hot gas rising from below the photosphere. As these gases rise to the photosphere, they spread out, cool, and descend again, creating a distinctive pattern that resembles grains of rice.
Each granule is typically about 700 to 1000 kilometers in diameter, quite large but still minuscule compared to the size of the Sun. This pattern is visible in detailed images captured by telescopes, such as those from the Japanese Hinode spacecraft and the Swedish Solar Telescope. The Doppler Effect can also be used to study the motions of granules by analyzing the spectral lines of gases above the photosphere.
To answer the student's question directly, the correct choice is: a) Granulation.