Radiometric dating exam questions
Choose your answers to the questions and click 'Next' to see the next set of questions.You can skip questions if you would like and come back to them later with the yellow "Go To First Skipped Question" button. Choose your answers to the questions and click 'Next' to see the next set of questions.• The decay constant is unique for each radioactive element. The Decay Constant, • Some values of the decay constant: • C14: 1.21x10-4 atoms per year • U235: 9.72x10-10 atoms per year • K40: 5.34x10-10 atoms per year Calculating a Half Life • t = (ln (P D)/P)/ • What is the half life of Carbon-14?• t = (ln ((1 1)/1))/1.21x10-4 • t = (ln 2)/1.21x10-4 • t = 5,730 years Some Half Lives • Carbon-14: 5,730 years • Uranium-235: 704 MY • Potassium-40: 1.3 BY • Uranium-238: 4.5 BY • Rubidium-87: 48.8 BY Calculating a Radiometric Date • t = ln (P D)/P (P D = starting material) l • An ash bed just above the Dev.- Carb.
Firstly, supernovae have not added a significant amount of new elements to putative star-forming clouds.Furthermore, there is evidence that the main radioactive elements were concentrated in a layer low in the mantle and came to the surface progressively after that.I emailed you about this topic a year or two ago, and I've since taken a class in radioisotope chemistry at UCI. Basis of the Technique • Radioactive elements “decay.” Decay occurs as an element changes to another element, e.g. • The parent element is radioactive, the daughter element is stable. • Usually protons and neutrons are emitted by the nucleus. • Carbon-14 is produced by cosmic ray bombardment of Nitrogen-14 in the atmosphere. Doesn’t matter how many atoms started, half will decay. • Radioactivity occurs when certain elements literally fall apart. Key Term • Half-Life: the amount of time for half the atoms of a radioactive element to decay.Boundary has a Pb207: U235 ratio of 0.4192 /- 0.0010 • t = (ln ((1 0.4192)/1))/9.72x10-10 • t = (ln 1.4192)/ 9.72x10-10 • t = 0.350 x 1.029x109 • t = 360,178,000 /- 859,000 years Setting the Radiometric Clock • When an igneous melt crystallizes, parent and daughter elements are chemically separated into different crystals.• Further radioactive decay keeps the parent and daughter elements in the same crystal.Professor Fowler did exactly this and has maintained his calculated radiometric age for the universe at about 10 billion years, with which I am basically in agreement.Interestingly, using these sorts of ratios, one piece of moon rock dated as being 8.2 billion years old, to the amazement of the dating laboratory involved.Because of this, and because the speed of light is in the numerator of every reduced radio decay rate equation, any changes in the speed of light are indicating changes in atomic decay rates. Importantly, the original short half-life elements were also a contributor and they have gone now.This also made for rapid heating of the earth interior (cool to start with).