题干

如图所示,烛焰在光屏上成清晰的像.下列哪个光学器材的成像原理与其相同(  )

A:投影仪

B:照相机

C:放大镜

D:近视眼镜

上一题 下一题 0.0难度 选择题 更新时间:2017-02-24 12:23:14

答案(点此获取答案解析)

B

同类题3

任务型阅读,阅读下列短文,根据短中的信息完成文后表格。(每空一词)

    Have you ever been so worried about something that you have a headache or even can't sleep at night? Then you cannot pay enough attention during a test or in your study. If so, then you know that is stress. You are worried too much about something. The bad feeling in your mind can make you angry, sad, or scared, and can even give you a stomachache or a headache.

    However, some kind of stress is good. You might feel excited when you are called to give a speech at school. You feel nervous but excited. This kind of stress can help you to get things well done. And you may do a better job in your test if the stress pushes you to prepare more beforehand(提前).

    On the other hand, bad stress can last long if you are unable to come over your problems. You may not feel well, if your parents are having a quarrel, if a family member is badly ill, if you're doing poorly at school, or if anything else makes you unhappy. That kind of stress isn't going to help you. And it can actually let you do worse in your daily life.

    The best way to fight the stress is to have a balanced life. Make sure you get enough sleep and eat properly. Have some regular exercise. You should take some time for fun. Get advice from your parents, teachers and friends. Soon after that, you'll probably get away with your stress.

Title:  Face the ____

Meaning of stress

Stress is a feeling if you ____ too much about something that you cannot solve.

Possible effect

You may feel ____ in your mind and body.

Different

kinds

Good stress

•You might feel ____ when you speak in public.

•You will do the job well.

•It makes you ____ more  before doing an important job.

 ____ stress

Stress can last long if you are ____ to come over your problems. It can actually let you do ____  in your daily life.

How to keep stress away

Keep a ____ life in mind. They are sleep, ____ , exercise, time for fun and talk with others.

同类题5

阅读材料,回答问题

柔性屏

    ①一言不合就掰弯手机,这不是一句玩笑。

    ②近日,某知名终端厂商在自家的科技大会上展示了他们生产的一款可折叠的变形手机。上网、看剧、收发邮件时,它是7英寸左右的平板电脑;打电话时,只需轻轻对折,就变成5英寸左右的智能手机。让手机实现可弯曲、可折叠功能的就是柔性屏。

    ③什么是柔性屏呢?柔性屏是柔性显示屏幕的简称,是随着显示技术的变革,在OLED(有机发光二极管)技术的基础上发展而来的。传统的显示屏都是以玻璃作为基板材料,柔性屏则是以塑料作为基板材料。玻璃是很难弯曲、折叠的,塑料则可以任意弯曲,柔性与刚性相对,主要是基板材料不同。

    ④目前人们常用的电脑、彩电、手机显示屏大多采用的是液晶显示技术(LCD),LCD显示屏就像三明治一样由两片玻璃夹着液晶材料,液晶可以调整光亮,但需要一种发光部件提供背光,因此需要背光源、偏光片、彩色滤光膜等繁复的零组件,这使得屏幕的厚度很难降下来。与液晶显示技术不同,柔性显示屏使用的是OLED技术,通过将一种粉末状的新型显示材料蒸镀到塑料基板上,通电后的屏幕就能发出不同颜色的光。因为实现了自发光,所以柔性显示屏不再需要背光源、彩色滤光片等部件,比LCD显示屏轻薄不少。

    ⑤柔性屏不仅在体积上更加轻薄,功耗上也更低,有助于提升设备的续航能力。同时对比度更高,在色彩亮度和清晰度上都有更优异的表现。柔性屏还能通过外力拉伸达到卷曲伸缩的效果,做到大小随意切换而不影响显示清晰度。此外,由于采用了塑料基板,柔性屏的耐用程度高于以往屏幕,能够降低设备意外损伤的概率。

    ⑥因此,柔性屏一问世就受到市场的热烈追捧。几家显示屏厂商宣布今年内将实现柔性屏的批量生产。

(人民网  2017.2.20有删改)