The sea is a place that many people yearn for, because she looks so blue and beautiful. But do you know why she is blue?

The reason why the sea appears blue is due to the action of sunlight. Sunlight consists of seven colors: red, orange, yellow, green, cyan, blue, and purple. The longer wavelengths of light in them are more easily transmitted into seawater and are easily absorbed by seawater or marine life. Most of the short wavelengths are reflected and scattered and fail to enter the seawater.

The color of water changes with the environment around the water. Dissolved elements or suspended impurities in the water may cause the water to produce different colors. Usually, the water we see seems to be colorless and transparent, because the amount of water is relatively small, and the water molecules that make up water absorb too little visible light, which can be ignored. Therefore, almost all visible light penetrates through the water, and the water naturally becomes transparent to our eyes.

So, when pure water reaches a certain depth, it will appear blue, and the deeper the water, the bluer it is, such as those huge ice blocks in the ocean and glaciers. When light penetrates deep seawater or ice, more and more red light is lost along the way. When it reaches a depth of several meters, most of the red light has been consumed, while the blue light can penetrate very far. Before being fully absorbed, blue light is free to scatter and reflect, and some of it eventually returns to the surface of seawater or ice, illuminating the blue light into our eyes.

Blue light itself is a kind of light that is good for the human body. It can help the body to regulate the biological clock, thereby improving the sleep cycle, but if used improperly, it may cause damage to the eyes. Nowadays, there are many sources of blue light, such as LED lights, computers, mobile phones, etc. The wavelength of blue light is relatively short and the energy is relatively high, which will aggravate the symptoms of eye fatigue and dryness, and even cause damage to the fundus, so you should wear anti-blue light glasses. At the same time, avoid looking directly at the LED light source for a long time, such as mobile phones or computers.

In addition to blue light, ultraviolet rays, lasers, etc. have different degrees of damage to the human eyes, so in our daily life, we need to pay attention to the following points:

1. Avoid staying outdoors for a long time during the peak period of ultraviolet radiation to reduce excessive sunlight exposure. The time of excess UV generally refers to 11:00 am to 2:00 pm.

2. Pay attention to the UV damage caused by the reflected light from the water surface, beach, road surface, etc. during outdoor activities.

3. When going out in the sun or driving, you should wear UV protective lenses that can protect UVA and UVB to protect your eyes. Sunglasses, according to the optical principle, the lens color is preferably dark brown or dark green.