Effects of refraction of light

Due to refraction of light, various effect are observed in our daily life. We have many advantages by the refraction of light. The following are some example of them:

1. A clear pool of water always appears to be shallower   than  it actually is.

2. A coin placed at the bottom of beaker containing water       seems it be raised.

3. A stick partially dipped in water seems to be sent.

4. The sun appears flattened at the time of sun set and sun rise.

5. The density of the air in the atmosphere is greater near the surface of the earth than above it. 

Thus, the magnitude of refraction increases with decreasing height. Due to this, the lower portions of the sun at the time of sun set and sun rise are raised more than the upper portions. Hence, the vertical diameter of the sun is shortened more than the horizontal diameter. As a result, the sun seems flattened.

The stars seem twinkling of light. The density of the layers of the atmosphere changes continuously. Due to the changes in the density of air, the magnitude of refraction of the light rays from the stars also changes continuously. This changes causes the apparent positions of the images of the stars to change continuously with time. Hence, the stars appear to twinkle.