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- University physics volume 3
- Unit 2. modern physics
- Nuclear physics
- Radioactive decay
Summary
- In the decay of a radioactive substance, if the decay constant (
) is large, the half-life is small, and vice versa.
- The radioactive decay law,
uses the properties of radioactive substances to estimate the age of a substance.
- Radioactive carbon has the same chemistry as stable carbon, so it mixes into the ecosphere and eventually becomes part of every living organism. By comparing the abundance of
in an artifact with the normal abundance in living tissue, it is possible to determine the artifact’s age.
Conceptual questions
Problems
A sample of radioactive material is obtained from a very old rock. A plot ln
A verses
t yields a slope value of
(see
[link] (b)). What is the half-life of this material?
The decay constant is equal to the negative value of the slope or
The half-life of the nuclei, and thus the material, is
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The half-life of strontium-91,
is 9.70 h. Find (a) its decay constant and (b) for an initial 1.00-g sample, the activity after 15 hours.
a. The decay constant is
. b. Since strontium-91 has an atomic mass of 90.90 g, the number of nuclei in a 1.00-g sample is initially
The initial activity for strontium-91 is
The activity at
is
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A radioactive sample initially contains
mol of a radioactive material whose half-life is 6.00 h. How many moles of the radioactive material remain after 6.00 h? After 12.0 h? After 36.0 h?
;
;
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An old campfire is uncovered during an archaeological dig. Its charcoal is found to contain less than 1/1000 the normal amount of
. Estimate the minimum age of the charcoal, noting that
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Calculate the activity
, in curies of 1.00 g of
(b) Explain why your answer is not exactly 1.00 Ci, given that the curie was originally supposed to be exactly the activity of a gram of radium.
a. 0.988 Ci; b. The half-life of
is more precisely known than it was when the Ci unit was established.
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Natural uranium consists of
,
and
,
What were the values for percent abundance of
and
when Earth formed
years ago?
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World War II aircraft had instruments with glowing radium-painted dials. The activity of one such instrument was
Bq when new. (a) What mass of
was present? (b) After some years, the phosphors on the dials deteriorated chemically, but the radium did not escape. What is the activity of this instrument 57.0 years after it was made?
a.
; b.
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The
source used in a physics laboratory is labeled as having an activity of
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?
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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
removed for reactor use and is nearly pure
. Depleted uranium has been erroneously called nonradioactive. To demonstrate that this is wrong: (a) Calculate the activity of 60.0 g of pure
. (b) Calculate the activity of 60.0 g of natural uranium, neglecting the
and all daughter nuclides.
a.
; b.
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Questions & Answers
the study of living organisms and their interactions with one another and their environments
AI-Robot
HOW CAN MAN ORGAN FUNCTION
the diagram of the digestive system
allimentary cannel
Ogenrwot
They formed in two ways first when one sperm and one egg are splited by mitosis or two sperm and two eggs join together
Oluwatobi
Genetics is the study of heredity
Misack
how does twins formed?
Misack
discuss biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles
the study of living organisms and their interactions with one another and their environment.
Wine
discuss the biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles in an essay form
list any five characteristics of the blood cells
Shaker
lack electricity and its more savely than electronic microscope because its naturally by using of light
advantage of electronic microscope is easily and clearly while disadvantage is dangerous because its electronic. advantage of light microscope is savely and naturally by sun while disadvantage is not easily,means its not sharp and not clear
Abdullahi
cell theory state that every organisms composed of one or more cell,cell is the basic unit of life
Abdullahi
is like gone fail us
DENG
cells is the basic structure and functions of all living things
Ramadan
is organisms that are similar into groups called tara
Yamosa
in what situation (s) would be the use of a scanning electron microscope be ideal and why?
A scanning electron microscope (SEM) is ideal for situations requiring high-resolution imaging of surfaces. It is commonly used in materials science, biology, and geology to examine the topography and composition of samples at a nanoscale level. SEM is particularly useful for studying fine details,
Hilary
cell is the building block of life.
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Source:
OpenStax, University physics volume 3. OpenStax CNX. Nov 04, 2016 Download for free at http://cnx.org/content/col12067/1.4
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