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
39
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/36sQKKKQ
相关试题推荐
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。 ADoctorintheHou...
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。 ADoctorintheHou...
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。 ADoctorintheHou...
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。
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。
下面的短文后有2项测试任务:(1)第23~26题要求从所给的6个选项中为第1~4段每段选择1个最佳标题;(2)第27~30题要求从所给的6...
下面的短文后有2项测试任务:(1)第23~26题要求从所给的6个选项中为第1~4段每段选择1个最佳标题;(2)第27~30题要求从所给的6...
下面的短文后有2项测试任务:(1)第23~26题要求从所给的6个选项中为第1~4段每段选择1个最佳标题;(2)第27~30题要求从所给的6...
下面的短文后有2项测试任务:(1)第23~26题要求从所给的6个选项中为第1~4段每段选择1个最佳标题;(2)第27~30题要求从所给的6...
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。 TheToughGrassth...
随机试题
血小板膜糖蛋白GPⅡa可以与哪种糖蛋白结合?( ) A.GPⅠa
内异症最常见的发生部位是 A.剖宫产后的切口 B.宫骶韧带 C.直肠子宫陷
下图为同样大小的正方体堆叠而成的多面体正视图和后视图,该多面体可拆分为①、②、③
农村留守儿童问题是我国经济社会发展中的阶段性问题,是我国城乡发展不平衡、公共服务
当市场中猪肉的价格上涨幅度过大,有可能影响城镇居民的生活水平时,政府一般可以采取
不同组织对采购需求的计算各不相同,主要包括()。
细菌性痢疾的确诊依据是A:粪培养阳性B:粪便镜检有大量脓细胞C:粪检有巨噬细胞D:粪便免疫学检查抗原阳性E:典型细菌性痢疾临床症状
以下关于过度正角化的描述,正确的是A:角化层增厚,角化细胞核消失B:角化层增厚,角化细胞核残留C:棘细胞层出现角化D:角化层未增厚,角化细胞核消失E:角
国内生产总值的计算方法中不包括( )A.生产法B.收入法C.倍数法D.支出法
下列条件不适合实行成本领先战略的是()。A:大批量生产的企业,产量达到经济规模B:企业有较低的市场占有率,严格控制产品定价和初始亏损,从而形成较高的市场份额