Scientists can determine the age of ancient objects by a method called radiocarbon dating. The bombardment of the upper atmosphe
re by cosmic rays converts nitrogen to 14C ,a radioactive isotope of carbon, with a half-life of about 5730 years. Vegetation absorbs carbon dioxide through the atmosphere and animal life assimilates 14C through food chains. When a plant or animal dies, it stops replacing its carbon and the amount of 14C begins to decrease through radioactive decay. Therefore, the level of radioactivity must also decay exponentially. A parchment fragment was discovered that had about 13% as much 14C radioactivity as does plant material on Earth today. Estimate the age of the parchment.
Select the correct answer.
a) t= 16,724 years
b) none of these
c) t= 17,150 years
d) t= 18,373 years
e) t= 16,866 years
f) t= 16,189 years
Select the correct answer.
a) t= 16,724 years
b) none of these
c) t= 17,150 years
d) t= 18,373 years
e) t= 16,866 years
f) t= 16,189 years
1 answer:
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Answer:
<em>Correct answer: B.</em>
Explanation:
Electrostatic Field
It measures the electric effect of a charge distribution in its surroundings. If we wanted to test or measure the electric field by using a point-charge of value q', then the electric field is
The electrostatic force between two point charges is
So, the electric field is
The theory shows that the electric field doesn't depend on the test charge used, i.e., if we now use q'=-q', the electric force will be of the same magnitude but in the opposite direction, thus the electric field will be the same. Let's recall the formula is used to compute the scalar value of the field, the direction must be studied separately.
Now, if we changed the test charge to another value, say 2q, the measured force will be
And the new electric field is
We can see the electric field is not affected by the value of the test charge.
Finally, if we move the test charge to another location and keep the same charge, the electric force will vary and the electric field will be different.
Correct answer: B.