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The phenomenon of advanced sunrise and delayed sunset is primarily caused by which of the following?
Atmospheric reflection
Atmospheric refraction
Total internal reflection
Dispersion of light
Atmospheric refraction
Advanced sunrise and delayed sunset occur because of the refraction of sunlight by the Earth's atmosphere. As sunlight enters the denser layers of the atmosphere, it bends towards the normal, allowing us to see the Sun even when it is physically below the horizon.
Advanced sunrise and delayed sunset occur because of the refraction of sunlight by the Earth's atmosphere. As sunlight enters the denser layers of the atmosphere, it bends towards the normal, allowing us to see the Sun even when it is physically below the horizon.
Think of a pencil placed in a glass of water that appears bent at the surface; the air-density gradient around Earth acts similarly, 'bending' the sunlight around the curvature of the planet.
R-A-D (Refraction = Advanced/Delayed)
╬ФtтЙИ2┬аminutes тАФ total time gain per sunrise or sunset event due to atmospheric refraction
╬╝=sinrsiniтАЛ тАФ Snell's law governing the bending of light at interfaces
The Earth's atmosphere consists of layers with varying optical densities, which increase as we get closer to the surface. When sunlight enters these layers, it undergoes atmospheric refraction, causing the rays to follow a curved path. This phenomenon results in an apparent shift in the position of the Sun, making it appear about 2 minutes earlier than its actual sunrise and 2 minutes later than its actual sunset.
Refraction is caused by the gradient in refractive index of the atmosphere.
The total difference in time observed due to this effect is approximately 4 minutes per day.
The Sun appears flat at sunrise and sunset due to similar refractive effects.
Explanation of apparent flattening of the solar disc
Understanding the discrepancy between astronomical and apparent sunrise/sunset times
The apparent shift in position is approximately 0.5┬░.
Option A is incorrect as reflection changes the direction of light back into the same medium.
Option C is incorrect as total internal reflection occurs only when light travels from a denser to a rarer medium at an angle greater than the critical angle.
Option D is incorrect as dispersion is responsible for the splitting of light into its constituent colors, like in a rainbow.
B is correct тАФ Atmospheric refraction causes light to bend as it passes through the layers of varying density in the atmosphere, creating the illusion of the Sun's position.
Remember that all 'apparent' changes in position of celestial objects (like stars twinkling or the Sun's flattened shape) are almost always due to Atmospheric Refraction.