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stealth61 [152]
3 years ago
5

Francium-223 has a half-life of 22 minutes. A Geiger counter gives a reading of 58 counts per minute (cpm) from a sample of fran

cium-223. What will the reading be 22 minutes later? You can ignore background radiation.
Physics
1 answer:
polet [3.4K]3 years ago
8 0

Answer:

29 counts per minute (29 cpm)

Explanation:

The half-life of a radioactive isotope is the time needed for the activity of the sample to halve.The half-life of Francium-223 is exactly 22 minutes: this means that its activity after 22 minutes becomes exactly half of its initial value. Since the initial activity of this sample of francium-223 was 58 cpm, the activity after 22 minutes will be

A=\frac{58 cpm}{2}=29 cpm

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icang [17]

Wave speed = (wavelength) x (frequency)

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                       =               8 m/sec

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Explanation:

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2 years ago
We want to design a cylindrical vacuum capacitor, with a given radius a for the outer cylindrical shell, that will be able to st
anastassius [24]

Solution :

a). Using Gauss's law :

  $E=\frac{Q}{4 \pi \epsilon_0r^2}$  ,    $b    .........(1)

Let $E=E_0,\ r=b$ in equation (1)

Therefore, $Q=4 \pi \epsilon_0b^2E_0$  .............(2)

$V_b-V_a = \int^a_b \vec E. d\vec l$

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            $=\frac{Q}{4 \pi \epsilon_0} \int^a_b \frac{1}{x^2} \ dx$

            $=\frac{Q(a-b)}{4 \pi \epsilon_0 a b}$  ....................(3)

Therefore, $U=\frac{1}{2}Q \Delta V$

                     $=\frac{1}{2}(4 \pi \epsilon_0 b^2 E_0)\left(\frac{Q(a-b)}{4\pi \epsilon_0 a b}\right)$

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Now differentiating the equation (4) w.r.t. 'b', we get

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Thus the radius for the inner cylinder conductor is $b=\frac{3}{4}a$

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$U = 4 \pi\epsilon_0 \frac{27a^3E^2_0}{512}$

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8 0
3 years ago
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zheka24 [161]

Answer:

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6. Planets may form within the protostellar disk that surrounds a forming star.

7. Mass can be lost through a jet of material ejected along a protostar's axis of rotation.

8. A "star" with mass below 0.08 solar mass has its gravitational contraction halted by degeneracy pressure.

8 0
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The answer is flight technology, satelite technology, and  exploration technology.

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