Why do mountaineers wear sunglasses?

Why do mountaineers wear sunglasses?
Mountaineers wear sunglasses to protect their eyes. In areas with low altitudes, the concentrated air and a certain amount of dust can absorb and block the sunlight, making the sunlight less intense; the air in the mountains above four or five kilometers above sea level is very thin, and the dust in the air is rare. The ability to absorb and block sunlight will be reduced accordingly, so the sun here is particularly strong. In addition, there are thick white snow on the slopes and peaks of the mountains, and white is the most reflective color. Even if you look down on the sun without looking down, you can’t hide the glare of the sun. If the eyes are unobstructed, strong infrared rays and ultraviolet rays will illuminate the retina of the eye, which will burn the visual cells. In severe cases, it will cause vision loss and even blindness.

The sunglasses worn by mountaineers are different from ordinary sunglasses. They not only block visible light in the sun, but also contain chemicals that absorb infrared rays and ultraviolet rays, which can fully protect the athlete’s eyes.

Why is there a code on the banknote and not on the coin?
Banknotes must have sufficient reserves before they can be issued. The banknotes of each country use foreign exchange reserves to support its currency. Since the foreign exchange reserves have a fixed number, the circulation of banknotes is also controlled, and the use of codes to calculate the circulation is a convenient method. In addition, as long as the banknote holder goes to the issuing bank, the bank that issues the banknotes is responsible for giving the holder the foreign exchange equivalent of “pay as you go”, so the banknote number also serves as statistical and anti-counterfeiting information.

Why is the flag almost purple?
There are more than 200 countries in the world. One of the common points in the design of the ever-changing and colorful national flags is that almost no “purple” is used.

This is because purple was a very expensive dye in the past and must be extracted from the mucilage of some conch. The process is extremely labor-intensive, and it takes more than 10,000 conch to refine 1 gram of dye. It only survives in the Terre region of the eastern Mediterranean. The price of this rare dye is much higher than that of the same period of gold. If it is to be used on a banner that must be printed in large quantities, it is not cost.

Until 1856, a British chemist developed a synthetic purple pigment.

The aniline violet and purple dyes were produced in large quantities and began to be widely used in the garment industry. Despite the popularity of purple, the flag of almost all countries was designed at the time, so it is almost impossible to see purple appearing on the national flag today.

There are exceptions, however, in the Republic of Nicaragua, Dominica, which opened the new flag in 1971 and 1978, and the Second Republic of Spain, which was founded in 1931 and died in 1931, all using purple on the national flag.

Why can cat eyes get bigger and smaller?
The muscle contraction on the cat’s pupil is particularly strong, just like a stretchy rubber band. When the light is strong, the muscles will push the pupils inward, and the pupils will become smaller. When the light is dark, the muscles will quickly pull the pupils out and the pupils will become larger. It turns out that the cat’s eyes will change and change because the cat’s pupil will change. Light enters the eye from the pupil. When the light is very bright, the cat will become smaller in order to protect the eyes, so that all the bright light will not run into the eyes; when the light is very dark, the cat’s pupil will become bigger and let more light Through the eyes, the eyes can see clearly.

Why does the refrigerator light turn on the freezer when it is turned on?

To answer this question, economists will inevitably compare the costs and benefits. Whether it’s in the freezer or in the freezer, the door will automatically light when the door is opened, and the cost is almost the same. This is what economists call “fixed costs.” From the perspective of revenue, there is a light in the cabinet, and it is more convenient for you to find things. Since most people open the freezer more often than there are open the freezer, it is clear that the benefits of installing a light in the freezer are greater. Therefore, since the cost of installing a lamp is the same, then according to the cost-effective principle, it is more cost-effective to install the lamp in the refrigerator than to install the lamp in the freezer.

Why can laptops operate under the power supply standards of the country?
At present, the household electricity provided by the US power system is 110 volts, and many countries have 220 volts. The notebook’s power cord has a built-in transformer that allows the computer to operate normally under both standards. However, televisions and refrigerators can only operate under one standard. To use a US refrigerator in France, you have to buy a separate transformer to convert the French 220 volt power supply to 110 volts. Why can’t these household appliances be used everywhere like laptops?

The built-in transformers for all appliances will undoubtedly meet this demand, but doing so will increase the manufacturing cost of the appliances. Most refrigerators, washing machines, televisions and other electrical appliances, I am afraid there will be no chance to travel abroad, so it is not reasonable to add extra expenses for the built-in transformers.

The laptop is an exception, especially during the time it was born. Most of the people who bought laptops at the time needed to bring business people who traveled around the world. For these people, carrying a heavy transformer on an international flight is an unacceptable burden. Therefore, laptop manufacturers have built-in transformers in their computers from the beginning.

What color is the moon?
After the sun is reflected by the moon, it passes through the Earth’s atmosphere. The atmosphere is like a protective shell, which is composed of many gases, and the sunlight is white light composed of seven main colors of red, orange, yellow, green, cyan, blue and purple.

The moon is like a mirror that reflects the light of the sun to the earth. When the night sky is relatively clear, the reflected light passes through the atmosphere, and the dust and small water droplets are less. The seven main colors are not blocked. In the eyes of the people, white light is seen, and this is the silvery white moon.

When the weather is not so good, the reflected light passes through the atmosphere, and there are more dust and small water droplets. The blue light, blue light and purple light in the sunlight are blocked, and the remaining light is mixed. Yellow.

Why is cola not in the square box?
Almost all soft drink bottles, whether glass or aluminum, are cylindrical. The milk box seems to be square, because square containers can use shelf space more economically than cylindrical containers. So why do soft drink manufacturers insist on using cylindrical containers?

If the milk container is cylindrical, we need a larger refrigerator. Even if most people drink milk directly from the box, the cost-effective principle also shows that they are unlikely to be sold in cylindrical containers. Yes, square containers do save space, but the space saved in a case of milk is clearly more cost-effective than in a soft drink. Most soft drinks in supermarkets are placed on open shelves, which are cheap. However, milk needs to be specially installed in the freezer. The freezer is expensive and the operating cost is high. Therefore, the storage space in the freezer is quite valuable, thus increasing the profit of loading milk in a square container.