Laser Beam Intensity: Solve W/m², J, & mm | Help Needed

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To determine the intensity of a laser beam used to burn cancerous tissue, first calculate the energy per area per time assuming 100% absorption, then adjust for 94% absorption by multiplying the result by 1/0.94. The area of the circular spot must be calculated using the diameter converted from mm to meters. After solving, one participant confirmed their answer was 1360 W/m² and estimated that the laser's intensity is about 10,000 times greater than direct sunlight. This discussion highlights the importance of proper unit conversion and understanding absorption rates in calculating laser intensity.
CMATT
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Thread moved from the technical forums -- poster has been reminded of the PF rules
What is the intensity in W/m² of a laser beam used to burn away cancerous tissue that, when 94.0% absorbed, puts 539 J of energy into a circular spot 2.11 mm in diameter in 4.00 s??

I've tried a couple different equations and I keep getting the answer wrong. This is due tonight, I'm super stuck. Any input is greatly appreciated
 
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First imagine the beam is 100% absorbed, find that answer, and multiply that answer by 1/.94 to get the answer for 94% absorbed. To get the 100% absorbed answer, just take that energy, per that area, per that time. You will have to convert mm to m though, and you will need to know the area of a circle.
 
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Ken G said:
First imagine the beam is 100% absorbed, find that answer, and multiply that answer by 1/.94 to get the answer for 94% absorbed. To get the 100% absorbed answer, just take that energy, per that area, per that time. You will have to convert mm to m though, and you will need to know the area of a circle.

Thank you for your help Ken G! I will try this out right now
 
Ken G said:
First imagine the beam is 100% absorbed, find that answer, and multiply that answer by 1/.94 to get the answer for 94% absorbed. To get the 100% absorbed answer, just take that energy, per that area, per that time. You will have to convert mm to m though, and you will need to know the area of a circle.

Yay I got the correct answer, thank you! Would you happen to know how this one below is solved? I did my answer - 1360 W/m^2, and got a number, but I'm not sure if that's correct:

How many times more intense is this than the maximum intensity of direct sunlight (about 1360 W/m²)?
 
A quick estimate says its about 10,000 times more for the laser. Is that about what you got?
 

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