1801年，托马斯·杨氏双缝干涉实验研究了光波的性质。1834年，洛埃利用单面镜同样得到了杨氏干涉结果（称洛埃镜实验）。
洛埃镜实验的基本装置如图所示，
为单光源，
为一平面镜。适用平面镜成像作图法画出经平面镜反射后的光与直线发出的光在屏上相交
的区域。
(2) 设光源到平面镜的垂直距离和到光屏的垂直 距离分别为
和
，光的波长为
，在光屏上形成干涉条纹。则相邻两条亮纹（或暗纹）间距离
的表达式为_______________。
Jim's uncle （eat）nothing yesterday evening．
He （not be）back home for five years．
It's very hot．The child doesn't mind （open）the window．
We often （think）understanding poems is hard．
If you pay a visit to Liu Hasheng's restaurant in Harbin，you will find 18 robots there．They are ready to serve you and make sure that your dining e（81） is perfect．After the visit，you can tell others that the robots serving customers isn't a dream any more．
It's wonderful to see h（82） the 18robots work in the restaurant．The wonder s（83） when you walk in．You'll see a robot come up and say，"Earth person，hello!Welcome to the Robot Restaurant．"When you have ordered your m（84） ，the robots in the kitchen begin to do the cooking．After the food is p（85） ，a robot waiter will glide （滑行） out of the kitchen to serve you with the meal you've ordered．And as customers enjoy their d（86） food，a robot sings lovely songs for them．
You may ask，"Where did all these robots come from？"Liu said they were designed （设计） and m（87） by the Harbin Haohai Robot Company．Liu said he invested （投资） 5million yuan in the restaurant，with each robot costing 200，000 yuan to 300，000 yuan．And the w（88） robot team is managed by the workers in the computer room．
After a busy day，all the robots will go for a"meal"，which is e（89） ．After 5 hours，the robots can continue their work for a day．The restaurant now provides a menu with more than 30 dishes （菜肴），and the average （平均） cost for a dinner is a（90） 40to 50yuan．Do you want to go and have a try in this restaurant？