Light Intensity: Calculating Energy Flux through an Area Element

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SUMMARY

The discussion focuses on calculating the energy flux of light intensity from a bulb rated at 40 W through a 40 cm² area element. The formula used is I = Power/Area, which simplifies to W = Pt when time is introduced. With a time duration of 4 seconds, the total energy calculated is 160 J. This highlights the importance of including time in energy calculations to derive meaningful results.

PREREQUISITES
  • Understanding of light intensity and energy concepts
  • Familiarity with the formula I = Power/Area
  • Basic knowledge of power units (Watts)
  • Concept of energy over time (W = Pt)
NEXT STEPS
  • Research the relationship between light intensity and energy flux
  • Learn about the implications of time in energy calculations
  • Explore different units of power and energy in physics
  • Study practical applications of light intensity in real-world scenarios
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Students in physics, educators teaching light and energy concepts, and anyone interested in understanding the calculations related to light intensity and energy flux.

davidphysics
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[SOLVED] Light Intensity question

The light (electromagnetic) output of a bulb is 40 W. How much energy passes through a 40 cm^2 area element aligned perp. to the light rays?

I know that I = Power/Area, but I thought that Power = W(aka. energy) /t , and the problem has no reference to time.

What am I missing?
 
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Without time this question is meaningless.
 
Yea we told our teacher, so now the t= 4 seconds, and obviously now the problem is super easy. W=Pt

W= 40 W (4 s)

W=160 J
 

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