首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Rubidium, potassium and carbon are three common elements used to date the history of Earth. The rates of radioactive decay of t
Rubidium, potassium and carbon are three common elements used to date the history of Earth. The rates of radioactive decay of t
admin
2013-11-29
33
问题
Rubidium, potassium and carbon are three common elements used to date the history of Earth. The rates of radioactive decay of these elements are absolutely regular when averaged out over a period of time; nothing is known to change them. To be useful as clocks, the elements have to be fairly common in natural minerals, unstable but decay slowly over millions of years to form recognizable "daughter" products which are preserved minerals.
For example, an atom of radioactive rubidium decays to form an atom of strontium (another element) by converting a neutron in its nucleus to a proton and releasing an electron, generating energy in the process. The radiogenic daughter products of the decay-in this case strontium atoms--diffuse away and are lost above a certain very high temperature. So by measuring the exact proportions of rubidium and strontium atoms that are present in a mineral, researchers can work out how long it has been since the mineral cooled below that critical "blocking" temperature. The main problems with this dating method are the difficulty in finding minerals containing rubidium, the accuracy with which the proportions of rubidium and strontium are measured, and the fact that the method gives only the date when the mineral last cooled below the blocking temperature. Because the blocking temperature is very high, the method is used, mainly for recrystallized (igneous or metamorphic) rocks, not for sediments--rubidium-bearing minerals in sediments simply record the age of cooling of the rocks which were eroded to form the sediments, not the age of deposition of the sediments themselves.
Potassium decays to form (a gas) which is sometimes lost from its host mineral by escaping through pores. Although potassium-argon dating is therefore rather unreliable, it can sometimes be useful in dating sedimentary rocks because potassium is common in some minerals which form in sediments at low temperatures. Assuming no argon has escaped, the potassium-argon date records the age of the sediments themselves.
Carbon dating is mainly used in archaeology. Most carbon atoms (carbon-12) are stable and do not change over time. However, cosmic radiation bombarding the upper atmospheres constantly interacting with nitrogen in the atmosphere to create an unstable form of carbon, carbon-14.
What is the common feature of rubidium, potassium and carbon?
选项
A、They can be made into clocks.
B、They are rich in content.
C、Their decay is slow but regular.
D、The products of their decay are the same.
答案
C
解析
文章第1段指出rubidium、potassium和carbon这三种元素的rates of radioactive decay of these elements are absolutely regular,并且decay slowly over millions of years,故选项C正确。
转载请注明原文地址:https://jikaoti.com/ti/6fOYFFFM
0
考博英语
相关试题推荐
Justiceinsocietymustincludebothafairtrialtotheaccusedandtheselectionofanappropriatepunishmentforthoseproven
Awayfromtheirprofession,scientistsareinherentlynomorehonestor______thanotherpeople.
ThestudyoflawhasbeenrecognizedforcenturiesasabasicintellectualdisciplineinEuropeanuniversities.However,onlyin
ThestudyoflawhasbeenrecognizedforcenturiesasabasicintellectualdisciplineinEuropeanuniversities.However,onlyin
Everycultureattemptstocreatea"universeofdiscourse"foritsmembers,awayinwhichpeoplecaninterprettheirexperience
Bondsincludegovernmentsecuritiesandcorporatebonds.Governmentsecuritiesareissuedbythefederalgovernmentorbyastat
OnecountrythatiscertainoftheeffectoffilmsontourismisAustralia.TheTouristOfficeofQueenslandsaythatCrocodile
FederalReserveBoardChairmanAlanGreenspanlaidforththeintellectualbasisforthelikelycontinuedaggressiveeasinginmo
Thereareavarietyofwaystothinkabouttheself.Twoofthemostwidelyusedtermsareself-conceptandself-esteem.Self-co
CaliforniansandNewEnglandersspeakthesamelanguageand______bythesamefederallaws.
随机试题
大隧之外,其乐也泄泄!泄泄:
按病证分类的方书首推
公开招标在开标时,应当由()。
某投资组合由A、B两只股票构成,已知A、B两只股票收益率的变化方向和变化幅度完全相同,则下列表述中,正确的有()。
密切关注、正确分析竞争对手的报价属于()。
RPI卡环的最佳适应证是()。
《宪法》在序言中明确规定:“本宪法以法律的形式确认了中国各族人民奋斗的成果,规定了国家的根本制度和根本任务,是国家的根本法,具有最高的法律效力。”同时规定:“全国各族人民、一切国家机关和武装力量、各政党和各社会团体、各企业事业组织,都必须以宪法为根本的活动
鸦片战争以后,西方列强野蛮入侵,封建统治腐朽无能,国家战乱不已,人民饥寒交迫,中国人民和中华民族遭受世所罕见的深重苦难。要实现民族独立、人民解放和国家富强、人民富裕,就必须推翻封建专制统治,对中国社会进行根本变革。辛亥革命的爆发,是()
A、Sheisworriedabouttheseminar.B、Themankeepsinterruptingher.C、Shefindsittoohard.D、Shelacksinterestinit.D原文重
玉饰不仅能使佩戴者更美丽,还能促进其身体健康。
最新回复
(
0
)