Energy flux density and and energy fluence question work shown

J*s) * (1.25 x 10^6 eV/1 photon) * (1.602 x 10^-19 J/eV)= 4.62 x 10^5 J/m^2The molar mass of Co-60 isotope does not directly affect these calculations. However, it does play a role in determining the number of photons emitted per second. Since the question specifies that the point source emits equal numbers of photons of 1.17 and 1.33 MeV, the molar mass is not needed in this particular scenario.In summary, to convert between photon units and joules, you can use the formula
  • #1
johnq2k7
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energy flux density and and energy fluence question! work shown please help!

A point source of Co-60 gamma rays emits equal numbers of photons of 1.17 and 1.33 MeV, giving a flux density of 5.7 x 10^9 photons/cm^2-sec at a specified location.

a.)What is the energy flux density there, expressed in J/m^2-min?
b.)What is the energy fluence of 1.17 MeV photons during 24 hours in J/m^2?

My work:

a.) 5.7 x 10^9 photons/cm^2-sec * (100 cm)^2/(1m^2)= 5.7 x 10^13 photons/m^2-sec
5.7 x 10^13 photons/m^2-sec * (60 sec/1min)= 3.42 x 10^15 photons/m^2-min

how do you convert photons/m^2-min to J/m^2-min for Co-60
do you find the rest energy of the molar mass which is 60 g/mol and multiply it by c^2

the correct answer is 685 J/m^2-min, how do you go from photons/m^2-min to J/m^2- min to find the energy flux density?


b.) 5.7 x 10^13 photons/m^2-sec * (86400 sec/24hr)= 5.7x10^13 photons/m^2

how do you convert photons/m^2 to J/m^2
the correct answer is suppose to be 4.62 x 10^5 J/m^2
how do you convert the photon units to joules
do you include the molar mass of Co-60 isotope some how

please help!











 
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  • #2




Thank you for your question regarding energy flux density and energy fluence. I will provide you with the steps to convert between photon units and joules, and also explain the role of the molar mass of Co-60 in these calculations.

a.) To convert from photons/m^2-min to J/m^2-min, you need to use the formula E = N*h*nu, where E is the energy in joules, N is the number of photons, h is Planck's constant (6.626 x 10^-34 J*s), and nu is the frequency of the photon in hertz. In this case, we have two different frequencies (1.17 and 1.33 MeV), so we will need to calculate the energy flux density for each separately and then add them together.

For 1.17 MeV photons:
E = N*h*nu = (5.7 x 10^9 photons/cm^2-sec * (100 cm)^2/(1m^2)) * (60 sec/1min) * (6.626 x 10^-34 J*s) * (1.17 x 10^6 eV/1 photon) * (1.602 x 10^-19 J/eV)
= 685 J/m^2-min

For 1.33 MeV photons:
E = N*h*nu = (5.7 x 10^9 photons/cm^2-sec * (100 cm)^2/(1m^2)) * (60 sec/1min) * (6.626 x 10^-34 J*s) * (1.33 x 10^6 eV/1 photon) * (1.602 x 10^-19 J/eV)
= 776 J/m^2-min

Therefore, the total energy flux density is 685 + 776 = 1461 J/m^2-min.

b.) To convert from photons/m^2 to J/m^2, we can use the same formula as above, but instead of multiplying by the number of minutes, we will multiply by the number of seconds in 24 hours (86400). We will also need to use the average energy of the two photon energies (1.25 MeV) in the calculation.

E = N*h*nu = (5.7 x 10^13 photons/m^2) * (86400 sec/
 

Related to Energy flux density and and energy fluence question work shown

What is energy flux density?

Energy flux density, also known as power density, is the amount of energy that passes through a unit area in a unit of time. It is measured in watts per square meter (W/m^2). In other words, it is a measure of how much energy is being transmitted through a given area.

What is the difference between energy flux density and energy fluence?

Energy flux density and energy fluence are both measures of energy, but they represent different aspects. Energy flux density is a measure of how much energy is passing through a unit area in a unit of time, while energy fluence is a measure of the total amount of energy that is delivered to a surface. Energy fluence is measured in joules per square meter (J/m^2).

How are energy flux density and energy fluence related?

Energy flux density and energy fluence are related by the time interval over which the energy is delivered. Energy fluence is equal to the energy flux density multiplied by the time interval. In mathematical terms, energy fluence (Φ) = energy flux density (S) x time interval (t).

Why is energy flux density important in understanding energy transfer?

Energy flux density is an important concept in understanding energy transfer because it allows us to quantify and compare the amount of energy being transferred through different materials or systems. It also helps us understand how energy is distributed and how it can be controlled or manipulated for various purposes.

How is energy flux density calculated and measured?

Energy flux density is calculated by measuring the amount of energy passing through a given area in a unit of time. This can be done using instruments such as pyranometers, which measure solar radiation, or calorimeters, which measure heat transfer. The energy flux density can also be calculated using mathematical formulas, such as P/A, where P represents power and A represents area.

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