LED lamps quickly and confidently entered our everyday life, their popularity is growing every year, and the cost of production is steadily declining. Since the issues of energy saving are relevant for everyone, replacing incandescent bulbs with LED ones is a matter of the near future. How to choose the right LED light sources?

Advantages, disadvantages and features of LED lamps

LED lamps or LED lamps have their own advantages and disadvantages, as well as features of use. The advantages are known to all: they consume little energy and their service life is more than 10 years, according to manufacturers. Additional pluses - they can be very small, do not heat up, work great in the cold, withstand vibration and shock, and the disposal of such light sources does not harm nature - they do not contain mercury, like fluorescent lamps.

The disadvantages include a rather high cost and the presence of a degradation effect. During operation, the LEDs lose their properties (degrade) and their brightness decreases. If the LED has lost more than 30% brightness, it is considered to be out of order. At high temperatures, this phenomenon is more pronounced.

Very often, the disadvantage of LED lamps is considered an unpleasant bluish tint of the glow of LED lamps. In fact, this is not a disadvantage - it is a feature. If such light is annoying, then you can always buy lamps with a warmer yellowish-white glow color.

The features also include the narrow focus of the glow of LED lamps. Yes, the LED emits in one direction. But the design of the lamp may include a different number of LEDs, may have a diffuser or do without it. A narrow beam is ideal for spotlights and hand-held flashlights, while for a chandelier it is better to choose light bulbs that give diffused light.

Features of light sources should not be considered disadvantages. You need to understand how to use them correctly. However, conventional incandescent bulbs also have a peculiarity - they get very hot. Powerful lamps are able to melt the plastic cover and even set it on fire. Despite this, they are used everywhere; it never occurs to anyone to put on a homemade paper or fabric lampshade.

For most of us, the question of price does not require discussion. Everything is clear here. There is money - why not buy LED lamps? View, evaluate and draw conclusions for yourself. No money - nothing to talk about, you need to find the cheapest incandescent bulbs and use them.

The topic of security is much more interesting. Health is most important, so everything that is known about the possible harm of LED radiation to a person should be found out before going to the store to buy economical light bulbs.

How is an LED lamp made?

An LED lamp is a fairly complex light emitting device. The source of radiation is LEDs - semiconductor devices that convert electrical energy into the world. They cannot be connected directly to the mains, so each lamp contains a board with built-in LEDs, an electronic driver for converting mains power, all this is built into a metal radiator for cooling. Outside, there is a base of a certain type for connecting to any standard lamp and a protective cap, matte or transparent, which usually serves to scatter light.

All LEDs, depending on chemical composition crystal, emit light of a certain shade. But not white. White is a mixture of all the colors of the spectrum. To obtain white light, different technologies are used:

• many red, blue and green LEDs are placed on one matrix, the radiation of which is mixed with a lens;
• cover blue or ultraviolet LEDs with a phosphor that absorbs and converts radiation into white light;
• yellow-green or green with red phosphor is applied to a blue LED, as a result of which two or three radiations are mixed, forming white or close to white light.

What color of radiation from a particular light bulb can be found on the scale on the package. The color temperature is indicated there in degrees Kelvin, and for convenience there is a color scale on which the color is marked. For most people, white light with a yellowish tint is comfortable.

What else is good to know

A different spectrum of radiation affects people, animals, plants in different ways. For example, the use of red and blue LEDs in combination allows you to create an emission spectrum that promotes accelerated plant growth. Such LED lamps are used in greenhouses.

Inexpensive phosphor-coated ultraviolet LEDs produce white light with a slightly bluish tint. Such a glow, oddly enough, activates human body, provokes an increased release of the hormone serotonin, which increases efficiency. But such artificial excitement leads to irritability, because a person needs to rest ... In the bedroom, such a light bulb would probably be inappropriate.

A big plus of LED lighting is that LED light does not flicker like daylight fluorescent lamps. However, this applies only to products high level with high-quality power supplies (drivers). Manufacturers of cheap light bulbs save money, their products pulsate no worse than fluorescent ones. This flickering cannot be noticed, but it has a harmful effect on vision. Read more about the safety of LED lamps at safetydom.net.

How to choose an LED lamp

Buying an LED lamp is not a problem. But there are many different ones. They differ in power and shape, in the base and in the shade of the glow. And the price is also different. What to take?

How to calculate lamp power

Each lamp is designed for lamps of a certain power and size, they must have an appropriate base, all other parameters are chosen at your discretion.

To make the room light, you can pre-calculate the power according to the norms, depending on the area of ​​\u200b\u200bthe room. Or pick up light bulbs "by trial and error." Since most of us know what power incandescent or "housekeeper" lamps are already in use, LED lamps are selected according to this table.

How to choose a lamp base

The base is the place where the light bulb is inserted or screwed into the lamp. When buying a new chandelier, they usually also buy bulbs for it in the same store. The seller will select and advise. When choosing for an old chandelier or sconce, they do this: they unscrew a light bulb from it and take it with them to the store. There are not so many types of socles, they can simply be remembered visually.

First and most importantly, well-known manufacturers of LED lamps supply the market with tested and certified products, give a guarantee for several years. Such light sources can be trusted, they are safe for health. It is better to give preference to popular brands, for example, Philips, Gauss, Kreonix, Shine, Verbatim, Panasonic, Osram, etc. All kinds of fakes are cheaper, but it is not known why they are cheaper. Whether they are harmful to health is also an unanswered question. Here are a few useful tips from site:

• Don't buy cheap lamps. The prices of different manufacturers of quality products are approximately the same. If the light bulb has the same parameters as the branded one, but its price is two times lower, pass by. This is a poor quality fake. She might not be safe.
• Check for flicker. You can conduct a simple experiment, namely, look at the lamp through digital camera. You can use your smartphone camera. A pulsed light (stroboscopic effect) is immediately visible on the screen. Example in this video:

Do you know how much it affects a person lighting? For example, scientists claim that the winter depression experienced by a significant number of people is caused by a lack of light. Thanks to the right lighting in the apartment, you can not only adapt more easily to the cold season, but also set yourself up for work, give evening gatherings with friends or family an atmosphere of comfort and fill the nursery. the maximum number light, properly combining natural and artificial lighting.

Organization lighting in the apartment implemented by choosing fixtures, their location, as well as lamps - direct light sources. In this article, you will learn how to choose the right color temperature for lamps, in other words, the shade of light.

Most often, three shades are distinguished:. So that we can give you some tips on which lamps with which shade of light will best suit a particular area.

Bedroom

The bedroom is a place where a calm, relaxed atmosphere should reign, because it is here that you relax and gain strength for the next day. Therefore, the lighting in this room should be soft, uniform and subdued. For this, it is best warm light lamps. If you are a fan of reading or working before going to bed, then in addition to the central lighting, you should additionally use a sconce with a lamp of a colder shade. To avoid strong contrast with the central light, designers recommend white light for this purpose.

Children's

In the event that you have a children's room, you probably know that a child needs a lot of light. Of course, it is best that as much sunlight as possible enters the room, but at night or cloudy weather, you will have to compensate for the lack of light with artificial lighting.

For the central lighting of the nursery, it is better to use white light bulbs. But accent lighting depends on the age of your child. For example, for children preschool age it is recommended to turn on a warm light lamp before going to bed, which will allow the child's body to rebuild for sleep. In the event that your child is a schoolboy, he needs a workplace to complete the lessons, and, therefore, a cold-colored table lamp, which will quickly help you get in the mood for work.

Hallway

The entrance hall creates the first impression of the apartment, so it is very important to choose the right lighting. If the light is dim, it is likely that this part of the apartment will be lost, and if it is too bright, it can blind the incoming person. Therefore, it is best to choose a neutral white shade of light. And remember that it is important to correctly position the light source of the mirror, otherwise you may dazzle the viewer.

Kitchen

Most often, the size and layout of the apartments do not allow separating the kitchen and dining room, so it is necessary to separate the working and dining areas. In many ways, this will help to make lighting.

Cooking requires bright accent lighting. For this, a cold shade is best suited. But, unlike the working area of ​​the kitchen, the dining table does not require bright light - everything is decided by your taste and preferences. If you like to sit up in the evenings with friends or family, then the warm subdued light will create an atmosphere of comfort at your table. And if the kitchen for you is just a place to satisfy your hunger, then it is better to use white lamps.

Living room

Lighting in the living room depends on how you spend time here. If you prefer to drink tea in the evening or look through magazines in a calm atmosphere, then warm light lamps will go for this. If this is a place where you gather with friends or family for a joint holiday and fun, you should light up the living room with neutral white lamps. For those who prefer to work or read here best solution there will be cold light.

Study/office

We often spend a considerable amount of time in the office, and this is where our eyes are most prone to fatigue. If you want to make the office as comfortable as possible, make sure that there are no strong differences in light and shadow in the room. The entire area should be well lit with cold light bulbs, - they are the most favorable for work.
The shade of light can also be selected depending on your interior. For a classic, warm tones will go, which will create an atmosphere of comfort, and for a modern one, it is better to choose a neutral white shade of light that can best recreate natural light. If you have a spacious interior, then you can safely use lamps with a cold shade, as they will fill your apartment with bright light.

The above tips are quite generalized, however, given them, you can not only beautifully, but also correctly illuminate all areas of your home. Remember that important factors such as performance, mood and health depend on the lighting you choose.

Article from here The secret of fast solidification of hot water is revealed and my comment is in red at the end of the article.

The phenomenon of hot water freezing faster than cold water is known in science as the Mpemba effect. Such great minds as Aristotle, Francis Bacon and Rene Descartes have pondered over this paradoxical phenomenon, but for millennia no one has yet been able to offer a reasonable explanation for this phenomenon.

Only in 1963, a schoolboy from the Republic of Tanganyika, Erasto Mpemba, noticed this effect on the example of ice cream, but none of the adults gave him an explanation. Nevertheless, physicists and chemists seriously thought about such a simple, but so incomprehensible phenomenon.

Since then, different versions have been expressed, one of which was as follows: part of the hot water simply evaporates at first, and then, when a smaller amount remains, the water solidifies faster. This version, due to its simplicity, became the most popular, but scientists were not completely satisfied.

The greatest minds of mankind have fought over the Mpemba paradox (Scott Akerman/Flickr).

Now a team of researchers from University of Technology Nanyang in Singapore (Nanyang Technological University), led by chemist Xi Zhang, said they have solved the age-old mystery of why warm water freezes faster than cold water. As Chinese experts found out, the secret lies in the amount of energy stored in hydrogen bonds between water molecules.

As you know, water molecules consist of one oxygen atom and two hydrogen atoms held together by covalent bonds, which at the particle level looks like an exchange of electrons. Another well-known fact is that hydrogen atoms are attracted to oxygen atoms from neighboring molecules - this forms hydrogen bonds.

At the same time, water molecules as a whole repel each other. Scientists from Singapore noticed that the warmer the water, the greater the distance between the molecules of the liquid due to the increase in repulsive forces. As a result, hydrogen bonds are stretched, and therefore store more energy. This energy is released when the water cools - the molecules approach each other. And the return of energy, as you know, means cooling.

The Mpemba effect illustrated in a graph (Wikimedia Commons illustration).

As the chemists write in their article, which can be found on the arXiv.org preprint site, hydrogen bonds are stretched more strongly in hot water than in cold water. Thus, it turns out that more energy is stored in the hydrogen bonds of hot water, which means that more of it is released when cooled to sub-zero temperatures. For this reason, freezing is faster.

To date, scientists have solved this riddle only theoretically. When they present convincing evidence of their version, then the question of why hot water freezes faster than cold water can be considered closed.

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Summer is joy and grace. But when the thermometer shows unthinkable numbers in the shade, it becomes sticky, wet and almost unbearable. In hellish heat it is difficult to be within the walls of an ordinary apartment, to fall asleep at night. Especially if there is no air conditioning.

website found working tricks that will help you feel comfortable at home, even if the temperature outside the window goes off scale.

Ice in front of the fan

chilled sheet

If the house is very hot even at night and it is impossible to fall asleep, then we put the sheet in the freezer for 10 minutes and only after that we lay it down. Don't forget to put the sheet in a plastic bag first. This will create a feeling of coolness during falling asleep, and not moisture.

Wet curtains

If you open a window and sprinkle curtains hanging on it with water from a spray bottle, then the effect of more humid and cool air is guaranteed. True, it will last up to half an hour. For a lasting effect, you need to spray the fabric quite often.

Closed windows and balcony

In order to cut off the hot air from the street and prevent the greenhouse effect, you just need to get rid of the habit of opening windows and a balcony door when it's hot. It is best to ventilate the apartment before the heat, in the earliest hours, and after it subsides, late at night.

Reflective film

The real barrier to sunlight- reflective mirror film on the windows. It is easily glued with your own hands, is inexpensive and effectively keeps the room cool.

Ceiling fan

A ceiling fan is an excellent remedy for the heat in an apartment. And in summer period it must rotate counterclockwise to create a cold air stream at high speed. This cool breeze effect will definitely help you feel good on the hottest days.

Several new plants

Plants help to keep the house cool, as they partially lose moisture in the process of processing moisture. Therefore, the air in a house with greenery is cleaner and fresher. Aloe vera, Areca palm, Benjamin's ficus, house fern, pike tail, golden pothos can especially help keep cool. True, you should remember about their frequent watering.

Ice bottles

Simple but effective method cool the house - put in the rooms water bottles that have been frozen in the refrigerator. The ice will melt and give off a damp coolness. Breathing will become much easier. All bottles can be refrozen after the ice has melted. And if the heat is unbearable, then such a bottle can be rolled with your feet. Feeling better instantly.

MOSCOW, September 15 - RIA Novosti. Scientists from Moscow State University and Japan have learned to almost instantly change the polarization of light and reduce its speed tenfold, which will help create light computers, ultra-fast displays and new computer networks, according to an article published in the journal Physical Review Applied.

"We have been working together with Professor Inoue for a long time, and during these fifteen years we have learned a lot about these amazing nanostructures. In our experiments with real crystals, we have achieved that light comes out of them about ten times later than if it were just in the air ", - says Tatyana Dolgova from the Moscow state university named after M.V. Lomonosov.

Dolgova, her colleagues at Moscow State University and physicists from the Toyohashi Technological University (Japan) achieved a similar effect thanks to the so-called magnetophotonic crystals - special structures that interact with light in a special way, changing its polarization, speed of movement and a number of other parameters.

The idea of ​​creating such a crystal, which is a set of optical resonators that "slow down" the movement of light through the crystal in a special way, was first proposed in 1998 by the Japanese physicist Mitsuteru Inoue, one of the authors of the article. Such "slowing down" of light, as explained by Dolgova, is necessary for the creation of holographic light memory, three-dimensional screens, and magnetic field sensors.

These crystals and the phenomena associated with them remained the subject of theoretical calculations for a long time until Dolgova, Inoue and their colleagues realized that such effects could be achieved using not ordinary optical resonators, but an effect discovered back in the 19th century by the British physicist Michael Faraday.

He discovered, observing light through a special prism that only allows rays of one polarization to pass through, that the light disappeared or dimmed if the lamp's rays passed through a magnet. In the language of physics, Faraday established that the plane of polarization of light rotates as it passes through a magnetized substance.

Using this effect, physicists from Moscow State University and Japan have achieved that the plane of polarization of "slow" light rotates so quickly that changes can be seen even with ultrashort laser pulses 200 femtoseconds long. (a femtosecond is one millionth of a nanosecond).

As scientists admit, this effect cannot yet be used to create supercomputers due to its low strength, but these limitations are not fundamental. Thus, Russian physicists have shown that ultrafast modulation of light in magnetophotonic crystals is possible and has more than good prospects.