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(a) The 210 Po source used in a physics laboratory is labeled as having an activity of 1.0 μ Ci size 12{1 "." 0 m"Ci"} {} on the date it was prepared. A student measures the radioactivity of this source with a Geiger counter and observes 1500 counts per minute. She notices that the source was prepared 120 days before her lab. What fraction of the decays is she observing with her apparatus? (b) Identify some of the reasons that only a fraction of the α size 12{α} {} s emitted are observed by the detector.

(a) 1.23 × 10 3 size 12{ {underline {1 "." "23" times "10" rSup { size 8{ - 3} } }} } {}

(b) Only part of the emitted radiation goes in the direction of the detector. Only a fraction of that causes a response in the detector. Some of the emitted radiation (mostly α size 12{α} {} particles) is observed within the source. Some is absorbed within the source, some is absorbed by the detector, and some does not penetrate the detector.

Armor-piercing shells with depleted uranium cores are fired by aircraft at tanks. (The high density of the uranium makes them effective.) The uranium is called depleted because it has had its 235 U removed for reactor use and is nearly pure 238 U . Depleted uranium has been erroneously called non-radioactive. To demonstrate that this is wrong: (a) Calculate the activity of 60.0 g of pure 238 U size 12{"" lSup { size 8{"238"} } U} {} . (b) Calculate the activity of 60.0 g of natural uranium, neglecting the 234 U and all daughter nuclides.

The ceramic glaze on a red-orange Fiestaware plate is U 2 O 3 and contains 50.0 grams of 238 U , but very little 235 U . (a) What is the activity of the plate? (b) Calculate the total energy that will be released by the 238 U decay. (c) If energy is worth 12.0 cents per kW h , what is the monetary value of the energy emitted? (These plates went out of production some 30 years ago, but are still available as collectibles.)

(a) 1.68 × 10 5 Ci

(b) 8.65 × 10 10 J

(c) $ 2.9 × 10 3

Large amounts of depleted uranium ( 238 U ) are available as a by-product of uranium processing for reactor fuel and weapons. Uranium is very dense and makes good counter weights for aircraft. Suppose you have a 4000-kg block of 238 U . (a) Find its activity. (b) How many calories per day are generated by thermalization of the decay energy? (c) Do you think you could detect this as heat? Explain.

The Galileo space probe was launched on its long journey past several planets in 1989, with an ultimate goal of Jupiter. Its power source is 11.0 kg of 238 Pu , a by-product of nuclear weapons plutonium production. Electrical energy is generated thermoelectrically from the heat produced when the 5.59-MeV α particles emitted in each decay crash to a halt inside the plutonium and its shielding. The half-life of 238 Pu is 87.7 years. (a) What was the original activity of the 238 Pu in becquerel? (b) What power was emitted in kilowatts? (c) What power was emitted 12.0 y after launch? You may neglect any extra energy from daughter nuclides and any losses from escaping γ rays.

(a) 6.97 × 10 15 Bq

(b) 6.24 kW

(c) 5.67 kW

Construct Your Own Problem

Consider the generation of electricity by a radioactive isotope in a space probe, such as described in [link] . Construct a problem in which you calculate the mass of a radioactive isotope you need in order to supply power for a long space flight. Among the things to consider are the isotope chosen, its half-life and decay energy, the power needs of the probe and the length of the flight.

Unreasonable Results

A nuclear physicist finds 1.0 μ g of 236 U in a piece of uranium ore and assumes it is primordial since its half-life is 2.3 × 10 7 y . (a) Calculate the amount of 236 U that would had to have been on Earth when it formed 4.5 × 10 9 y ago for 1.0 μ g to be left today. (b) What is unreasonable about this result? (c) What assumption is responsible?

Unreasonable Results

(a) Repeat [link] but include the 0.0055% natural abundance of 234 U with its 2.45 × 10 5 y half-life. (b) What is unreasonable about this result? (c) What assumption is responsible? (d) Where does the 234 U come from if it is not primordial?

Unreasonable Results

The manufacturer of a smoke alarm decides that the smallest current of α radiation he can detect is 1.00 μ A . (a) Find the activity in curies of an α emitter that produces a 1.00 μ A current of α particles. (b) What is unreasonable about this result? (c) What assumption is responsible?

(a) 84.5 Ci

(b) An extremely large activity, many orders of magnitude greater than permitted for home use.

(c) The assumption of 1.00 μA is unreasonably large. Other methods can detect much smaller decay rates.

Questions & Answers

find the 15th term of the geometric sequince whose first is 18 and last term of 387
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The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
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kinnecy Reply
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I'm not sure why it wrote it the other way
I got X =-6
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Commplementary angles
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a perfect square v²+2v+_
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algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
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rolling four fair dice and getting an even number an all four dice
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Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
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No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
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Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
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. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
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abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
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Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
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what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
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silver nanoparticles could handle the job?
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I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
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Source:  OpenStax, College physics -- hlca 1104. OpenStax CNX. May 18, 2013 Download for free at http://legacy.cnx.org/content/col11525/1.1
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