A:这群氢原子只能发出三种频率不同的光,其中从n='3' 跃迁到n=2所发出的光波长最短
B:金属钠表面所发出的光电子的初动能最大值为9.80eV
C:金属钠表面所发出的光电子的初动能最大值为11.31eV
D:这群氢原子只能发出两种频率不同的光,其中从n=3跃迁到n=1所发出的光频率最高
唐朝是我国诗歌创作的黄金时代。下列诗句中,哪一句出自“诗圣”之手( )
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根据短文理解,选择正确答案。
English words don't stay the same. People need new words for new ideas and new inventions. Different words come into use, or old words are used in a new way.
English can be changed by borrowing words from other languages. The word “tomato” was borrowed from Mexico and “tea” came from China and so on. Now new space and science words are being borrowed from other countries, too. New words can be formed by adding two words together. “Countryside” and “earthquake” are made up of two parts. Sometimes new words are shorter forms of old words. The word “photo” was made from “photograph” by cutting off the end of the longer word. “Plane” was made by cutting off the front part of “airplane”. The names of people and products can become new words, too. Our “sandwich” was named after a man called Sandwich and “sellotape”(透明胶带) was a name given by the company that first made the product.
如图是干燥、收集某气体的装置,由实验装置可以推测该气体的有关性质.请你在表中找出相对应的选项( )
气体性质\序号
A
B
C
D
溶于水中所得溶液的pH
>7
<7
其密度(ρ1)与空气密度(ρ2)比较
ρ1>ρ2
ρ1<ρ2
ρ2<ρ1
在水中的溶解度
极易溶
难溶