The correct Answer is Atmospheric refraction
Explanation
The phenomenon of light bending as it passes from one medium to another is known as refraction. When light travels through the Earth's atmosphere, which has varying densities, it undergoes atmospheric refraction.
Statement-wise Analysis
- Scattering of light by aerosols - Incorrect
Scattering of light by aerosols is responsible for phenomena like the blue color of the sky and the reddish appearance of the sun at sunrise and sunset. It does not cause the sun to be visible before its actual rise.
- Atmospheric reflection from clouds - Incorrect
Reflection from clouds involves light bouncing off cloud particles. While clouds can reflect sunlight, this phenomenon does not explain the sun's apparent visibility before it physically crosses the horizon.
- Atmospheric refraction - Correct
The Earth's atmosphere has layers of varying optical densities. As sunlight enters the atmosphere, it passes from a rarer medium (space) to a denser medium (atmosphere). This causes the light rays to bend towards the normal. Since the atmospheric density increases closer to the Earth's surface, the light rays from the sun bend continuously. This bending makes the sun appear to be higher in the sky than its actual position. Consequently, the sun becomes visible approximately two minutes before it actually rises above the horizon.
- Diffraction at the horizon - Incorrect
Diffraction is the bending of light waves around obstacles or through openings. While diffraction occurs, it is not the primary phenomenon responsible for the apparent early sunrise. The effect of diffraction on the sun's apparent position is negligible compared to refraction.
Key Takeaway
Atmospheric refraction, caused by the varying optical densities of the Earth's atmosphere, is responsible for the apparent early sunrise and delayed sunset.