Interference of Light - Variations in Intensity

[mattmt]

We perceive intensity as the mod square of the electric field of light. As this electric field is varying sinusoidally then should we not see the interference fringes in a double slit diffraction pattern also vary sinusoidally in intensity as a result (albeit very quickly at the frequency of the light source)?

 

[Drakkith]

I believe the EM wave transfers energy at a constant rate, giving a constant intensity instead of a varying intensity. I'm not sure on the details though.

 

[Dale]

If it did, we would not see it.

http://en.wikipedia.org/wiki/Flicker_fusion_threshold
http://en.wikipedia.org/wiki/Frequency#Light

 

[mattmt]

So you are saying that it would oscillate but just too quickly for us to visually measure? Is there some other way that this effect could be detected?

 

[Dale]

Not with visible light, but you could easily do it with slower waves like water waves. Double slit interference works with pretty much all kinds of waves.

 

[Drakkith]

So you are saying that it would oscillate but just too quickly for us to visually measure? Is there some other way that this effect could be detected?

Not with visible light, but you could easily do it with slower waves like water waves. Double slit interference works with pretty much all kinds of waves.

The intensity wouldn't vary, because intensity is a measure of power, which is energy transfer over time. This does not vary.