1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Vinvika [58]
2 years ago
7

Smoke detectors fall into two major classes. Ionization detectors, the most common units, contain two parallel electrodes that a

re typically separated by 3 cm with a 5-V potential difference across them. The air molecules between the electrodes are ionized by collisions with helium nuclei that are produced by a radioactive source. Most units are initially fueled with 60 million nuclei of radioactive americium 241 (half-life 430 years). The now-ionized air molecules drift toward one of the electrodes with an average speed of 0.1 m/s and thus support a small current between the two electrodes. Smoke particles that enter and combine with the ions reduce the current and initiate an alarm.
Photoelectric detectors, by contrast, contain a light-emitting diode that sends a beam of unpolarized light across a small chamber. The light beam usually has a wavelength of 6.0 × 10–7m and has an intensity of 1.0 × 10–3 W. When smoke particles enter the chamber, the light scatters in all directions. A photocell then senses either the increase in the scattered light or the reduced intensity of the light beam and sets off the alarm. The speed of light in air is 3.0 × 108 m/s.
Ionization detectors respond faster to the large smoke particles of flaming fires; photoelectric detectors sense the small particles of smoldering fires more quickly. Modern units have both types of detectors.
When fewer than 3.75 × 106 americium nuclei remain, the ionization smoke detector will not operate due to insufficient ionization. How much time will pass before there are this many nuclei remaining?
a. 1720 years
b. 2150 years
c. 4300 years
d. 6880 years
Physics
1 answer:
bonufazy [111]2 years ago
7 0

Answer:

1720 years is the amount of time that will pass.

Option a) 1720 years is the correct answer

Explanation:

Given the data in the question;

 Number of nuclei initially N₀  = 60 million = 60,000,000

After time t, Number of nuclei remaining N_{rem = 3.75 × 10⁶

Also given that; half-life of radioactive americium t_{1/2 = 430 years.

so;

λ = ln2 / t_{1/2

we substitute

λ = ln2 / 430 years

N_{rem = N₀e^(-λt)

solve for t

t = 1/λ × ln( N₀/N_{rem  )

so we substitute

t = 1 / (ln2 / 430 years) × ln( 60,000,000 / ( 3.75 × 10⁶ ) )

t = ( 430 years / ln2 ) × ln( 60,000,000 / ( 3.75 × 10⁶ ) )

t = ( 430 years / 0.693147 ) × ln( 16 )

t = 620.359 years × 2.7725887

t =  1720.0003 ≈ 1720 years

Therefore, 1720 years is the amount of time that will pass.

Option a) 1720 years is the correct answer

You might be interested in
An element has the following natural abundances and isotopic masses: 90.92% abundance with 19.99 amu, 0.26% abundance with 20.99
sashaice [31]

<u>Answer:</u> The average atomic mass of the given element is 20.169 amu.

<u>Explanation:</u>

Average atomic mass of an element is defined as the sum of masses of the isotopes each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

\text{Average atomic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i     .....(1)

We are given:

  • For isotope 1:

Mass of isotope 1 = 19.99 amu

Percentage abundance of isotope 1 = 90.92 %

Fractional abundance of isotope 1 = 0.9092

  • For isotope 2:

Mass of isotope 2 = 20.99 amu

Percentage abundance of isotope 2 = 0.26%

Fractional abundance of isotope 2 = 0.0026

  • For isotope 3:

Mass of isotope 3 = 21.99 amu

Percentage abundance of isotope 3 = 8.82%

Fractional abundance of isotope 3 = 0.0882  

Putting values in equation 1, we get:

\text{Average atomic mass}=[(19.99\times 0.9092)+(20.99\times 0.0026)+(21.99\times 0.0882)]

\text{Average atomic mass}=20.169amu

Hence, the average atomic mass of the given element is 20.169 amu.

4 0
3 years ago
Why do areas north of the artic circle in tje northern hemisphere experience a polar day lasting for several months during summe
adell [148]
<span>The regioin is titled towqrd the Sun during polar day.  (C)

(The same exact thing happens in areas south of the Antarctic Circle 
in the southern hemisphere.  The only difference is that the whole thing
is spelled better in the South.)</span>
7 0
3 years ago
Read 2 more answers
True or false. The planet's speed never changes. That is why we have a stable orbit.
Svetradugi [14.3K]
This answer is true the earth always stays at one speed
8 0
2 years ago
Magnets attract objects made up of _______;_______and _______​
mixas84 [53]
I think metal, steel and copper.
3 0
2 years ago
A car is traveling up a hill that is inclined at an angle θ above the horizontal. Determine the ratio of the magnitude of the no
padilas [110]

Explanation:

The weight of the car is equal to, W_c=m\times g...........(1)

Where

m is the mass of car

g is the acceleration due to gravity

The normal or vertical component of the force is, F_N=mg\ cos\theta

or

F_N=mg\ cos(13).............(2)

The horizontal component of the force is, F_H=mg\ sin\theta

Taking ratio of equation (1) and (2) as :

\dfrac{F_N}{W_c}=\dfrac{mg\ cos\theta}{mg}

\dfrac{F_N}{W_c}=cos(13)

\dfrac{F_N}{W_c}=0.97

or

\dfrac{F_N}{W_c}=\dfrac{97}{100}

Hence, this is the required solution.

5 0
3 years ago
Other questions:
  • A string is wrapped several times around the rim of a small hoop with radius 8.00 cm and mass 0.180 kg. The free end of the stri
    12·2 answers
  • How can hypotheses best be tested
    11·1 answer
  • Energy transfer by convection is usually restricted to what type of substance?
    15·2 answers
  • A series circuit that is connected to a 50 V, 60 Hz source is made up of 25 ohm resistor, capacite wieh X= 18 ohms, and inductor
    13·1 answer
  • An object in projectile motion will follow which path? a]curved up from the ground b]curved down toward the ground c]straight do
    5·2 answers
  • 9. A car driver brakes gently. Her car slows down front --
    11·1 answer
  • Las placas de un capacitor de placas paralelas están en forma horizontal. En el espacio se coloca una losa de material dieléctri
    14·1 answer
  • Potential difference is measured in which units?<br> volts<br> amps<br> currents<br> watts
    8·2 answers
  • A stone tumbles into a mine shaft strikes bottom after falling for 3.8 seconds. How deep is the mine shaft
    11·1 answer
  • Need help with # of protons
    9·2 answers
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!