Light Intensity: Calculating Energy Flux through an Area Element

[davidphysics]

[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?

 

[astrorob]

Without time this question is meaningless.

 

[davidphysics]

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