00:00I don't know if you have noticed that sometimes it seems there is a pool of water on the road ahead,
00:05but it disappears when you walk closer. When you look up, the pool of water appears further ahead
00:11again. You walk forward, and it keeps moving. What is going on with this strange, fake water
00:17phenomenon? In fact, this is a mirage, an optical refraction phenomenon. Especially in the hot
00:24summer, when the sun shines on the ground, the road surface absorbs more heat, which heats the
00:30surface air, making the air density near the ground thinner. The higher the air is, the lower
00:37the temperature is relative to the lower part. The air density here is also greater than the hot air
00:43near the ground, which produces different dense media and forms a density gradient.
00:49The propagation speed of light in different media is also different. Therefore, when the light
00:56propagates from the denser cold air above to the thinner hot air below, it bends due to the
01:02different propagation speeds. However, our brain and eyes think that the line of sight and the
01:08light are a straight line. When the line of sight and the light refracted by the bending are greater
01:14than the critical angle, it will not refract, but will be totally reflected. So at this time, you
01:21see those inaccessible water surfaces. In fact, it is the result of total internal reflection of light
01:28through different dense media to your eyes, and those water surfaces are also reflections of the
01:33sky. Similarly, when the air is cold at the bottom and hot at the top, such as on the sea surface,
01:40an upper mirage will be formed. The upper and lower mirages have another familiar collective
01:46name, which is the fata morgana. Like and follow for more informative videos.
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