首页
财务会计
医药卫生
金融经济
考公考编
外语考试
学历提升
职称考试
建筑工程
IT考试
其他
登录
职称考试
下面的短文后列出了 7 个句子,请根据短文的内容对每个句子做出判断:如果该句提供的是正确信息,请选择A ; 如果该句提供的是错误信息,请选择B ; 如果该...
下面的短文后列出了 7 个句子,请根据短文的内容对每个句子做出判断:如果该句提供的是正确信息,请选择A ; 如果该句提供的是错误信息,请选择B ; 如果该...
admin
2020-12-24
48
问题
下面的短文后列出了 7 个句子,请根据短文的内容对每个句子做出判断:如果该句提供的是正确信息,请选择A ; 如果该句提供的是错误信息,请选择B ; 如果该句的信息文中没有提及,请选择C。
Radiocarbon Dating
Nowadays scientists can answer many questions about the past through a technique called radiocarbon (放射性碳), or carbon-14, dating. One key to understanding how and why something happened is to discover when it happened.
Radiocarbon dating was developed in the late 1940s by physicist Willard F. Libby at the University of Chicago. An atom of ordinary carbon, called carbon-12, has six protons(质子)and six neutrons(中子)in its mKJteus(原子核).Carbon-14, or C-14, is a radioactive.
unstable form of carbon that has two extra neutrons. It returns to a more stable form of carbon through a process called decay ( 衰减). This process involves the loss of the extra neutrons and energy from the nucleus.
In Libby’s radiocarbon dating technique, the weak radioactive emissions (放射) from this decay process are counted by instruments such as a radiation detects and counter. The decay rate is used to determine the proportion of C-14 atoms in the sample being dated.
Carbon-14 is produced in the Earth’s atmosphere when nitrogen (氮)-14,or N-14, interacts with cosmic rays (宇宙射线). Scientists believe since the Earth was formed,the amount of nitrogen in the atmosphere has remained constant. Consequently, C-14 formation is thought to occur at a constant rate. Now ratio of C-14 to other carbon atoms in the atmosphere is known. Most scientists agree that this ratio is useful for dating items back to at least 50, 000 years.
All life on Earth is made of organic molecules (分子) that contain carbon atoms coming from the atmosphem. So all living things have about the same ratio of C-14 atoms to other carbon atoms in their tissues (组织). Once an organism (有机体) dies it stops taking in carbon in any form, and the C-14 already present begins to decay. Over time the amount of C-14 in the material decreases, and the ratio of C-14 to other carbon atoms goes down. In terms of radiocarbon dating, the fewer C-14 atoms in a sample, the older that sample is.
Radiocarbon is reliable in dating an object back to at least 50,000 years.
选项
A Right
B Wrong
C Not mentioned
答案
A
解析
转载请注明原文地址:https://ti.zuoweng.com/ti/3ElQKKKQ
相关试题推荐
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有5处空白,短文后有6个句子,其中5个取自短文,请根据短文内容将其分别放回原有位置,以恢复文章原貌。 Mt.DesertIs...
下面的短文有5处空白,短文后有6个句子,其中5个取自短文,请根据短文内容将其分别放回原有位置,以恢复文章原貌。 Mt.DesertIs...
随机试题
试述门市的结构类型及特点。门市的结构类型及特点是:(1)二级管理结构。这是一种最简单的扁平组织结构,只有两个纵向层次,决策权集中在一个人手中。通常适合于员工很少
一、背景 某大剧场由建筑公司承担其项目总承包管理,剧场有地上10层,地下3层
(390-394题共用备选答案) A.0°~90° B.0°~125° C
B
小红是个乐观开朗的孩子,乐于助人,和同学关系很好,学习很努力。最近总是一个人发呆
(2013年)当前在我国拥有大规模用户群的“微信”、“微博”,均属于()应用。
D[考点]链霉素的作用机理和副作用[分析]链霉素是广谱氨基苷类抗生素,对结核杆菌有杀菌作用。能干扰结核菌的酶活性,阻碍蛋白合成。链霉素的副反应有对第8对颅神
一均质杆AB重W=30N,长100cm被悬于竖直的两墙之间,不计摩擦,则墙面的反力为()。 A.NA.=NB.=10kNB.NA.=NB.=20
在运动技能形成的泛化阶段学生的动作表现为( )A.僵硬、不协调B.顺利、连贯C.协调、流畅D.准确、优美
已知:甲公司股票必要收益率为12%,目前的股价为20元,预计未来两年股利每年增长10%,预计第1年股利为1元/股,从第3年起转为稳定增长,增长率为5%。 ...