题干

关于下列光学现象,说法正确的是(   )

A:水中蓝光的传播速度比红光快

B:光从空气射入玻璃时可能发生全反射

C:摄影机镜头镀膜增透是利用了光的衍射特性

D:分别用蓝光和红光在同一装置上做双缝干涉实验,用红光时得到的条纹间距更宽

上一题 下一题 0.0难度 选择题 更新时间:2018-02-11 03:42:23

答案(点此获取答案解析)

D

同类题1

阅读理解

    Could smells affect your lifespan? Female fruit flies (果蝇) without the ability to smell food live longer than other fruit flies.The sense of smell may be connected to the cellular ageing (细胞老化) process in many other living things  even people.Such connection has recently been found in both worms and flies.For example, scientists found that removing fruit flies' ability to smell made them live nearly 20 percent longer than flies with a sense of smell.

    They confirmed that food smells were the ones most likely to affect ageing, as nutrition (营养) and lifespan are known to be connected in many living things.To test the idea that food smells affect lifespan, they removed flies' ability to smell carbon dioxide, which is produced by some fly foods.They left the rest of the smelling system.

    This action had no effect on male flies, but the females lived 30 percent longer than normal.Removing the ability to smell CO2 may stop flies getting information about food availability.This could mean that food is not enough, causing processes that encourage flies to survive.Scientists found that the female flies from stored extra fat and that both males and females immune (免疫) to CO2 were stronger against the stress than normal flies.It is suggested that females may simply be easily influenced by the smells of CO2.

    Scientists point out that people don't know whether ageing and smell are connected in animals and humans.But they clearly experience physical changes after smelling food.

同类题4

根据短文理解,选择正确答案。

    Dolphins (海豚) live in a dark underwater world. It's often impossible to see each other or anything else around them, so sound plays an important role in their survival. To communicate with each other, dolphins produce all kinds of sounds.

    Only other dolphins understand what the sounds mean. Scientists haven't uncovered their secret communication, except for one kind of whistle. It might last less than a second, but this whistle is a big deal. Why? Because these whistles are actually names of dolphins — and every dolphin has one. Scientists call these sounds a “signature whistle.” When other dolphins hear the whistle, they know which dolphin is calling.

    Dolphins often hunt by themselves but still need to stay connected to the group. Since they can't always see each other, dolphins use their signature whistles to check in with other dolphins hundreds of yards away. “In coastal areas, dolphins exchange whistles even when they're a third of a mile apart,” says Greg Campbell, who studies animals. That means dolphins shout out to group members that might be nearly five football fields away.

    What's amazing is who names the baby dolphin. Not the mother. Not an auntie dolphin or another group member. Scientists believe the baby dolphin itself comes up with the signature whistle. Like human babies, a baby dolphin plays with sounds throughout its first year. While testing its sound skills, a baby dolphin is doing something amazing. It's creating or figuring out its signature whistle. How or why it chooses its signature whistle is not clear. Studies show that most of the time the signature whistle is nothing like its mother's or group members' whistles.

    When the baby dolphin is about a year old, its signature whistle is set. It repeats it often so the other dolphins learn to recognize it.

    Deciphering(破译) dolphin names is just the beginning of figuring out what dolphins communicate about. Do they chat about sharks? Discuss the tides? Maybe they even have a name for people. Someday scientists are to decipher the rest of dolphins' communication.