PTE考生目前最大的问题之一就是练习题缺乏。除了有限的基本官方书（PLUS，Testbuilder, OG）之外就没有题了。很多英语基础不是很扎实的同学很难找到练习材料。悉尼文波雅思PTE培训学校专门为澳洲，尤其是悉尼、墨尔本的PTE考生准备了适合PTE听力阅读练习的科学60秒。各位PTE同学可以练习PTE听力中的summarise spoken text和PTE口语中的retell lecture，PTE听力口语-科学60秒-Frosty Moss练习记笔记技巧和复述。废话少说，下面开始：
This is Scientific American — 60-Second Science. I’m Christopher Intagliata.
LEDs use only a quarter the energy of incandescent bulbs. But despite their efficiency, there isone thing they‘re not that good at: “They have a hard time giving directional light.” SangamChatterjee, a physicist at the University of Marburg and the University of Giessen, in Germany.
Chatterjee and his colleagues may have fixed that. They devised a highly focused, but stillenergy–efficient light beam, by starting with something that’s already a highly focusedbeam: a laser. The key is what they shoot the laser at: a substance with a particularstructure. “I‘m always tempted to say “white powdery substance” but I guess there’s someconnotation on that.”
They synthesized the material from cages of tin and sulfur atoms decorated with hydrocarbonmolecules. The laser–produced infrared light — which the human eye cannot see — goes in,but what comes out are many different optical wavelengths. “It’s a molecular light converter. Itbasically changes the color of the light, while retaining the directionality of the lasers. So youcan make something like a white laser beam containing many, many colors.” That mix ofcolors, overall, glows bright white, like a halogen bulb in a beam. The study is in the journalScience.
This sort of low–energy focused white beam could be used for the very small — like a lightsource for microscopes — to the very big. “You could use this for a spotlight in the theater. Andin the end it should be much more energy efficient than the typical standard spotlight.”Meaning focused white light…that takes a little heat off the environment.
Thanks for listening Scientific American — 60-Second Science Science. I’m ChristopherIntagliata.
