The correct option is 2 only
Explanation
Atmospheric refraction is the bending of light as it passes through the Earth's atmosphere. The atmosphere consists of layers with varying optical densities, generally increasing towards the Earth's surface. As light from extraterrestrial sources enters the atmosphere, it undergoes continuous refraction.
Statement-wise Analysis:
- Statement 1 is Incorrect: Light from a star travels from a rarer medium (vacuum) to a denser medium (Earth's atmosphere). As a result, the light rays bend towards the normal. The observer perceives the light as coming from a straight line along the final direction of the ray entering the eye. This causes the apparent position of the star to be slightly higher (elevated) than its actual position. This effect is maximum near the horizon.
- Statement 2 is Correct: The physical conditions of the atmosphere, such as temperature and air density, are not stationary but fluctuate continuously. Consequently, the refractive index of the air varies over time. This leads to a wavering path of light, causing the apparent position of the star to fluctuate slightly rather than remain constant. This fluctuation is the primary cause of the "twinkling" of stars.
Key Takeaway:
Atmospheric refraction raises the apparent altitude of celestial objects, while atmospheric turbulence causes fluctuations in their apparent position and brightness (twinkling).