【推荐1】White light is made up of a mixture of different colors. Light travels in waves, and different colors have different wavelengths. Things seem a particular color because of the light they reflect or scatter[散射]—a leaf appears green because it reflects green light. 

Scattering Light 

Shine a torch through an empty glass or bottle and look at the colour of the light in the bottle. Hold a piece of paper on the other side of the bottle and look at the colour of light that has passed through. Fill the glass or bottle with water and shine the torch through it. What colour is the light passing in the bottle or glass, and what colour is the light on the paper? Add a drop or two of milk and mix it thoroughly, and shine the torch through it again—what happens to the light in the glass or bottle, and the light on the paper？ 

Particles in suspension reflect light— this is called the “Tyndall Effect” （think of how car headlights reflect off fog, which is a suspension of water droplets in air）.

Light travels directly through water, with little reflection and scattering, and the colour does not change. Milk in water is a suspension of fat and protein particles[微粒] in water. The suspended particles should change the colour of the light in the bottle or glass to a bluish[带蓝色的] tinge[淡色], with the light on the paper having a reddish tinge. 

The blue part of the light （shorter wavelength） from the torch should be reflected and scattered by the particles in the suspension， more than the red, orange and yellow parts of the light （longer wavelength）. When this scattered light reaches people’s eyes, it makes the mixture seem blue, particularly at the edges. The particles allow more of the red, orange and yellow light through, so the light on the paper will have more of these colours in it. 

The light at the centre of the glass or bottle may also seem to have a reddish tinge—this is because it has passed through more particles than the light at the edges, so more of the blue light has been scattered away. 

Blue Skies 

Air molecules[微粒] also affect light. They absorb the light and then release （scatter） it in another direction. This is called the “Rayleigh Effect”. Air molecules absorb and release blue light more often than red, orange and yellow light. As this light is scattered, it reaches people’s eyes, making the sky seem blue. The red, orange and yellow light carries straight on without being scattered by the air molecules, so people do not see as much of it.

【推荐3】Pain is usually connected to a nervous system. When you put your hand too close to a hot stove, nerve cells send a warning of danger to your brain.     1     That, in turn, causes you to pull your hand away before any serious damage is done. Plants don’t have nerves or brains, so they can’t feel pain like you do.

    2     And since they can’t escape a potentially dangerous situation, they need other ways of fighting back.

The biggest threat to a plant’s life is getting eaten. Some plants discourage plant-eaters from chewing on them by growing thorns or sharp little hairs, like a rose or a cactus does. Other plants produce bad-tasting or even toxic chemicals.     3    

But a plant called bittersweet nightshade does something even more smartly. When a slug, a small creature, chews holes in a nightshade’s leaf, a kind of sweet juice begins dripping out of the edges of the wound, almost as if the plant were bleeding.     4     In their quest to collect the juice, the ants gather all over the injured nightshade plant and attack anything that stands in their way - including the slug that damaged the plant in the first place. In short: Slug attacks plant; plant calls army of ants to come closer to kill slug. Thus, the plant can help itself by calling the enemies of its own enemies.

    5     But they have armies of cold-blooded killers always ready to obey their orders.

【推荐3】More than the challenge of fitting into a new culture, there are many benefits that a student can get from an exchange program. These benefits include:

·Diverse academic opportunities. In fact, students want to study abroad rather than travel.     1     Instead, it will be the supply of diverse opportunities for the student. For example, the student will be able to experience the differences of teaching methods, educational formats and academic program offerings.

·    2     Studying in another country opens the student’s eyes to different surroundings, which makes the student know about the country’s customs, people and regions. Knowing other culture also teaches the student how to be open-minded.

·Personality development.     3     Thus, the student needs to make decisions on his or her own and suffer the consequences or enjoy the fruits of those decisions. With this, the student is taught how real life is, what it means to be responsible, and how being resourceful can help in his or her survival. It’s no wonder that most students who return after the exchange program are seen with significant improvement on their personal development.     4    

So, why not let your child have the benefits of a student exchange program? Exchange programs or study-abroad programs are a great investment for the student.     5     Just imagine, by transforming students in a foreign country, the society is starting to build new blood of more mature people who might just be able to create a better tomorrow for the generations to come.

【推荐2】Art museums are places where people can learn about various cultures. The increasingly popular “design museums” that are opening today, however, perform quite a different role. Unlike most art museums, the design museum shows objects that are easily found by the general public. These museums sometimes even place things like fridges and washing machines in the centre of the hall.

People have argued that design museums are often made use of as advertisements for new industrial technology. But their role is not simply a matter of sales—it is the honour of excellently invented products. The difference between the window of a department store and the showcase in a design museum is that the first tries to sell you something, while the second tells you the success of a sale.

One advantage of design museums is that they are places where people feel familiar with the exhibits. Unlike the average art museum visitors, design museum visitors seldom feel frightened or puzzled. This is partly because design museums clearly show how and why mass-produced products work and look as they do, and how design has improved the quality of our lives. Art museum exhibits, on the other hand, would most probably fill visitors with a feeling that there is something beyond their understanding.

In recent years, several new design museums have opened their door. Each of these museums has tried to satisfy the public’s growing interest in the field with new ideas. London’s Design Museum, for example, shows a collection of mass-produced objects from Zippo lighters to electric typewriters to a group of Italian fish-tins. The choices open to design museums seem far less strict than those to art museums, and visitors may also sense the humorous part of our society while walking around such exhibits as interesting and unusually attractive toys collected in our everyday life.

【推荐3】True happiness lies in rewarding relationships, not material wealth, according to new research. Scientists have said that a close circle of friends and family is most important for happiness, and that owning things such as iPhones, computers, being wealthy and owning a sports car do not provide the same level of satisfaction.

The study was done by psychologists at the Sahlgrenska Academy and Lund University, in Sweden. The experts analyzed articles in Swedish newspapers published in 2016 and recorded which words most often occurred in the same articles as the Swedish word for happiness. In this way, they could know our common happiness.

Co-author Dr Danilo Garcia, a researcher at the Sahlgrenska Academy’s Center for Ethics, Law and Mental Health, said, “It’s relationships that are most important, not material things that we possess, and this is in line with other findings in happiness research.”

The study, which contained more than 1.5 million words, showed that terms such as “grandmother” and personal pronouns such as “you”, “me”, “us” and “them” often emerge in the same article as the Swedish word for happiness. Researchers found that words such as “iPhone”, “millions” and “Google” almost never appear with the word “happiness”.

The study is a part of a larger research project on how people describe both positive and negative events in their lives. The researchers believe that the word analysis reflects a common perception among the members of our society as to what should make us happy.

Dr Danilo Garcia said, “Just as the Beatles sang, most people understand that money can’t buy you happiness or love. But even if we can understand the importance of close and warm relationships at a social level, it isn’t certain that everyone is aware that such relationships are actually necessary for our own personal happiness.”