Why are the tiles in the swimming pool blue

Because a chemical of copper sulfate is added to the swimming pool. Anhydrous copper sulfate is a white powder, but when it is dissolved in water, it will form a blue copper sulfate solution.

However, although copper sulfate looks blue, the national standard stipulates that the copper sulfate added in the swimming pool is 0.25 ~ 0.5 mg / L. According to the specified dosage, copper sulfate with a concentration of 1.0 mg / l will not dye the whole pool of dozens or even thousands of cubic meters of water blue. In fact, the blue in the swimming pool is related to the different degrees of absorption of light by water. The natural light we see is composed of seven light waves: red, orange, yellow, green, blue, indigo and purple. When the water is a little deeper, it will preferentially absorb red, orange and yellow, and more reflect green, blue and indigo, and the deeper the water is, the more blue it reflects. In other words, water can reflect blue into your eyes, so what you see is blue, and the blue in deep water is deeper than that in shallow water.

The first consideration is to approach people's visual habits, so that the pool water looks clear, transparent and cleaner. Therefore, there are many places to decorate the pool bottom and wall in blue. Because the water in nature is mostly blue due to the light reflection principle, the blue water is more in line with people's visual effect, which makes people relaxed and happy and feel like getting close

Secondly, in order to ensure the cleanliness and hygiene of the swimming pool, disinfectant should be added to the water. The common is copper sulfate. Because the water will be blue, the bottom of the pool itself will use blue color, which will not give people who do not know the situation a sense of fear. Of course, this is also the reason why the pool water will show light blue even if it is not decorated with blue

Third, the pool water is blue, which is easy to distinguish from the surrounding environment, which is more conducive for people on the shore or in the stands to observe the water. Blue itself is also the color of water reflecting natural light, so it can avoid interference with the visual effect. In this way, whether the audience and the referee observe the results and performance of competitors in the swimming pool bricks, or when the swimming pool is open to the public at ordinary times, The lifeguard has a good grasp of everyone's safety in the pool