从水面上方向水池中望去．看到的水的深度比实际的浅．从水面上看水中的鱼的位置比鱼的实际位置靠近水面．水的实际深度叫实深；眼睛看到的深度叫视深，它们之间的的关系可由折射规律来说明．如图１所示，Ｏ是池底的一点，ＯＡ、ＯＢ是从Ｏ点射向冰面进入人眼的两条光线，由于 Look in the direction of the pool from the water. The depth of water seen is shallower than it actually is. From the water surface, the position of the fish in the water is closer to the water than the actual position of the fish. The actual depth of water is called deep; the depth seen by the eyes is called apparent depth, and the relationship between them can be explained by the law of refraction. As shown in Figure 1, O is a point at the bottom of the pool. OA and OB are the two rays that shoot from the O point to the ice and enter the human eye.