Light Intensity: Calculating Energy Flux through an Area Element

AI Thread Summary
The discussion addresses a light intensity calculation involving a 40 W bulb and a 40 cm² area element. The formula for intensity, I = Power/Area, is highlighted, but confusion arises regarding the absence of a time reference in the initial problem. Once a time duration of 4 seconds is introduced, the calculation becomes straightforward, leading to the conclusion that 160 joules of energy pass through the area in that time. The importance of including time in energy calculations is emphasized. Ultimately, the problem is resolved by applying the formula W = Pt.
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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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